Building stones of Baltimore, the Monumental City
Published:January 01, 2015
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Joseph T. Hannibal, David W. Bolton, 2015. "Building stones of Baltimore, the Monumental City", Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015, David K. Brezinski, Jeffrey P. Halka, Richard A. Ortt, Jr.
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Baltimore, the Monumental City, was founded in 1729. One of the oldest large cities in the United States, it has had a long history of stone use. This chapter discusses the stone used for a number of iconic Baltimore monuments and buildings, including the Battle Monument, the Washington Monument, the neo-classical Basilica of the Assumption, the neo-Gothic Mount Vernon Place United Methodist Church, Transamerica Tower (Baltimore’s tallest building), and a number of other structures, providing an overview of the major stone types used in the city during the nineteenth and twentieth centuries. The general trend over this time is a shift from use of local and regional stone to use of stone from a variety of sources, including stone from Europe and Asia. This trend is most apparent in stone used for building exteriors. The various stones used have different properties, which affect their susceptibility to weathering. These include serpentinites, marbles, and brownstones that are particularly prone to weathering.
Baltimore, founded in 1729, has historically been one of the most important cities on the East Coast. Early on, the city was a major port for transatlantic trade, owing to its location adjacent to Chesapeake Bay. It was also a transportation hub for movement of goods to and from the Ohio valley and westward via the Baltimore and Ohio Railroad, completed in 1857. Geologically, Baltimore is located at the boundary between the unconsolidated Coastal Plain sediments of Cretaceous and younger age to the south and east and the igneous and metamorphic rocks of the Piedmont to the north and west. This boundary, called the Fall Line because of the rapids and waterfalls that limit upstream navigation of the major rivers on the East Coast, influenced the location of several cities along the East Coast, including Trenton,New Jersey (the Delaware River), Philadelphia, Pennsylvania (the Schuylkill River), Richmond, Virginia (the James River), and Washington, D.C. (the Potomac River). Paleozoic and older igneous and metamorphic rocks are exposed in Baltimore and to its north and west, and are in places capped by Cretaceous-age sediments. A number of these regional rocks were utilized as building stones in Baltimore, notably the older igneous rocks, serpentinite, and marble.
Early structures built in Baltimore, however, tended to be built of wood and brick. It was only at the beginning of the nineteenth century that Baltimore experienced what Maynard (2002, p. 234) has called an “explosive development of stone quarrying and distribution.” A number of stone types from the surrounding area were used for various purposes. By virtue of its location, Baltimore also had access by sea to quarries along the East Coast. Port Deposit Gneiss and Baltimore Gneiss (Jones Falls granite) were used for Fort McHenry (completed in 1800), as was Aquia Creek sandstone quarried in Stafford County, Virginia (McGee and Woodruff, 1992). Local Ellicott City Granite and Woodstock Granite (also known more accurately as Woodstock Quartz Monzonite) were used for buildings and paving stones. Baltimore’s Cathedral (completed in 1821), now named the Basilica of the Assumption (Stop 3), utilized both Ellicott City Granite and Aquia Creek sandstone.
The most celebrated stone used in Baltimore, however, was the Cockeysville Marble, quarried north of Baltimore. This marble was used for the Battle Monument (Stop 10), completed in 1825, and the Washington Monument (Stop 5), which was completed in 1829. These and other monuments erected in the city led to Baltimore being called The Monumental City. By the 1840s to 1850s, the marble had become very popular in Baltimore. It was used extensively to build the stone front steps of row houses and office buildings in Baltimore (Anonymous, 1924, p. 18; Bowles, 1939, p. 205). The Beaver Dam quarry at Cockeysville (Fig. 1) has also furnished marble for many buildings in Baltimore and Washington, including the 108 columns in the wings of the National Capitol. In the mid-1800s, at least 13 quarries were operating in the region. Today, the Cockeysville Marble is used primarily for crushed stone and high-purity calcite (Kuff and Brooks, 1985).
In mid-century and thereafter, the development of the railway system, changes in tariffs, and international trade agreements, led to the importation of a greater amount of foreign stone. This included stone from the Maritime Provinces of Canada used for portico columns of the Basilica of the Assumption in the 1860s.
The report on building stones for the 10th (1880) U.S. Census (Hawes et al., 1884, p. 281-282) provided a snapshot of stone used in Baltimore near the end of the nineteenth century. By that time much Connecticut and New Jersey sandstone (Triassic brownstones), Maine and Virginia granite, and ballast stone, all available via salt-water and canal transportation, had been used in the city. Local stone used included Cockeysville Marble and Maryland granite from Ellicott City, Woodstock, and Jones Falls. And railroad connections allowed access to more distant Chester County, Pennsylvania, serpentinite and Ohio sandstone (Berea Sandstone quarried in northern Ohio). The report also notes the use of Ulster County, New York, bluestone, quarried near and shipped out of the town of Rondout, situated on the Hudson River, for sidewalks. That report also included a perceptive chapter by Alexis Julien (1884) that warned that marble would not stand up well in cities.
Not long after the publication of the census report, the great stone expert George Merrill (1854-1929) listed eight important stone structures in Baltimore in two key works on building stone (Merrill, 1889, appendix 4; 1891, appendix 3). Five of these structures (including City Hall, Stop 9) were made of Cockeysville Marble. One building, First and Franklin Presbyterian Church (located at 210 West Madison Street), was made of Triassic New Brunswick, New Jersey, brownstone (Merrill, 1889, appendix 4; Zanow and Johnston, 2010, p. 87). And two structures were made with Maryland gneiss, the Baltimore jail using gneiss from Jones Falls (noted under Stop 5), and the Catholic Cathedral (now called the Basilica of the Assumption, Stop 3) using stone from Ellicott City.
The stone industry was well established in Baltimore by the later nineteenth century. Circa 1880 there were 41 marble and stone-cutting businesses in Baltimore, the best known of which was that of Hugh Sisson (1820-1893) (Scharf, 1881, p. 421). Sisson was also president of the Beaver Dam Marble Company and did stonework for the Baltimore City Hall.
By the turn of the century, improvement of transportation networks resulted in the availability of a greater variety of stone types. Except when disrupted by war and the Great Depression, the number of building stones, especially decorative stones, continued to grow. Hummelstown brownstone quarried in the Triassic Hammer Creek Formation near Hummelstown, Pennsylvania, for instance, was used for exteriors (Stone, 1932, p. 127), and a wide assortment of stones was used for interior decorative work. The availability of various stones can be traced in articles and advertisements in industry magazines such as Stone (originally published in Indianapolis, then other cities, 1888-1972), and Through the Ages (published in Baltimore, 1923-1932).
Baltimore’s architectural history was punctuated by the Great Baltimore Fire of 7-8 February 1904. The fire started on a Sunday morning and burned for 30 hours. This fire, which originated near the current location of the Royal Farms Arena (Howard and Lombard Streets), destroyed more than 1,500 buildings in 140 acres (70 city blocks). Getting the fire under control was hampered by freezing temperatures, high winds, and incompatibility of hose fittings used by different fire services. The area was rebuilt over the next few years; interestingly, rather than incorporating a new architectural aesthetic into the rebuilding process, the rebuilt area closely resembled the original area in appearance (Hayward and Shivers, 2004, p. 237).
A number of stone buildings survived the Great Baltimore Fire of 1904. An article in Through the Ages noted the ability of marble to withstand high heat, illustrating the marble-fronted International Trust Company Building, as it stood amongst blocks of charred rubble after the fire (Anonymous, 1925a, p. 8). A publication by the National Fire Protection Association (1904, p. 36), however, noted that the marble on that building was “badly chipped and practically useless.” The Indiana Limestone Quarrymen’s Association (1923, p. 26) illustrated the National Union Bank Building after the fire, noting that the Indiana limestone façade, damaged mostly by the collapse of adjacent buildings, was subsequently “put into first-class condition for a few hundred dollars.” This was despite the National Fire Protection Association’s (1904, p. 34) previous determination that the façade was badly damaged. Marble and calcareous limestone’s calcination temperature is 800 °C (Winkler, 1997, p. 246), but the Indiana Limestone Quarrymen’s Association (1923, p. 27) claimed that its stone could withstand greater temperatures without damage. Porosity can affect the susceptibility of a stone to fire damage (Sippel et al., 2007, p. 150), and Indiana limestone has a much greater porosity than does marble, so it is possible that that limestone would suffer less damage than marble. Granite, composed of several minerals with differing properties, was also affected by the fire. Damage due to the Baltimore fire included spalling and failure of internal stone columns (National Fire Protection Association, 1904, p. 66, 104). The National Fire Protection Association concluded (1904, p. 121) that marble and granite was “especially susceptible to damage.” It is important to note, however, that their definition of marble included many stones that are geologically limestone but which are called marble in the stone trade. And, of course, fire affects wood and metal as much as, or more than, stone.
By the 1920s Salem Limestone (Indiana limestone) became the choice stone in North America for office towers and monumental structures (e.g., the War Memorial Building, Stop 7, dedicated in 1925). This was in part due to the development of the industry in Indiana, and in part due to price differences in stone types. The Enoch Pratt Free Library picked Indiana limestone over marble because of cost (Enoch Pratt Free Library, 1928). The peak of Indiana limestone production was in 1928-1929 (Patton and Carr, 1982, p. 5). The Great Depression decreased the demand for stone, but its use gradually rose as the economy improved after the Second World War. The advent of thinner-wall cladding for the exterior of large buildings in the 1970s resulted in a great growth in the use of stone, both domestic and international, for tall office buildings. The stops included in this guidebook show a general trend over time in stone use: sources, especially for exterior stone, increased over time from local to regional, and then international sources.
Baltimore, with its local source rocks and ready access to overseas sources in Europe and Asia, has been a regional center for stone-related businesses. One of the largest of these in the late nineteenth century was the Hilgartner Marble Company, a company that remains in Baltimore today. (The former marble showroom of Hilgartner Marble is in the Tremont Grand complex, a former Masonic Grand Lodge, at 225 North Charles Street.) The publications office of the National Association of Marble Dealers was in Baltimore until their magazine, Through the Ages, ended its run in 1932, as the Great Depression took its toll on the stone industry (which at first was not affected by the Depression because there were orders for building stone to be filled that had been placed before the onset of the Depression in late 1929).
This chapter builds upon an earlier work, Sherry McCann-Murray’s (2001) “A geologic walking tour of building stones of downtown Baltimore, Maryland.” It also builds upon previous field trips in the region, particularly those in nearby Washington, D.C. (Doe, 1989). Those interested in this topic should also see Kuff and Brooks’s (1985) brochure on Maryland building stones and Livingston et al.’s guide to the stones of the National Mall (2015; this volume), which is in many ways complimentary to this chapter.
Rock Types and Names for Stone Used in This Guide
In this chapter commercial names of stones are set in italics (e.g., Indiana limestone) in order to distinguish these commercial terms from rock-unit names and names of rock types (e.g., Salem Limestone). This is necessary to avoid confusion, especially since commercial names are replete with synonyms and homonyms and stone designations that are not geologically accurate (Anonymous, 1912; Hannibal, 2014, p. 41-42). Formal rock units (e.g., Salem Limestone) have the first letter of their component words capitalized. Various names and other information on the major stones discussed under the stops below are summarized in Table 1. These stones include a wide variety of igneous, metamorphic, and sedimentary rocks from a number of localities in North America, Europe, and Asia.
Field Trip Stops
The stops in this chapter (Fig. 2) are arranged so that a walking trip can begin and end at the Inner Harbor. Stops, however, can be visited in any order. The interior of many of the sites can also be accessed, but days and hours of opening vary from site to site, and special arrangements may need to be made in some cases. Names of buildings are also subject to change.
Visitors may notice that street orientation is not aligned exactly with true north. When the town was first surveyed in 1732, Phillip Jones Jr., the town’s original surveyor, did not adjust his readings to convert magnetic north to true north (Hall, 1912, p. 15; Roylance, 1997). As a result, most of Baltimore’s streets are skewed ~3 degrees west of true north (currently , magnetic declination in Baltimore is ~11 degrees west).
Stop 1. Transamerica Tower (100 Light Street):Spanish Pink granite and Persian Red travertine
Transamerica Tower (100 Light Street) is located between East Lombard Street and E. Pratt Street. The building, formerly known as the Legg Mason Tower, was completed in 1973. At 161 m and 40 stories, it is Baltimore’s tallest skyscraper. Most of the exterior (Fig. 3) is clad with Spanish Pink granite (Gunts, 2003, p. 2C), a pink granite with a relatively high content of light gray quartz and a low amount of ferromagnesian minerals, mostly biotite. Pink orthoclase is the dominant mineral in the stone, giving the stone its pink coloration. The stone is from enormously productive quarries near Porrino, which is in Galicia, NW Spain (Fernández, 2003), near its border with Portugal. The stone is also known by the more accurate name Rosa Porriño granite. It is Late Carboniferous in age. This has been a relatively inexpensive stone (Richter and Simmons, 2004), that has been widely used in Europe and especially North America. Because of the low price, it was one of the stones investigated by the United States International Trade Commission (1987, p. A-24) over allegations that stone production was subsidized in Spain and Italy and so was being sold for less than fair value in the United States.
A number of tall buildings in the United States have been clad with this stone. Although this stone has been described as a “tough stone that can cope well with environmental conditions in major cities” (Price, 2007, p. 222), there have been problems with cladding in some cases, particularly due to anchoring systems used to hold the stone in place. It was only in the 1970s that such thin stone cladding became popular. Problems with the anchoring system of the stone façade of the Transamerica Building became apparent soon after construction in the 1970s. X-rays and drilling were used to determine problem areas and stone slabs were re-anchored when necessary. The Justice Center in Cleveland, Ohio, another tower clad with the same stone, and completed in 1977, also had problems, and many exterior panels had to be replaced within 20 years of installation (Hannibal and Schmidt, 1994, p. 34). Cracks can be currently seen in the stone used for the Transamerica Tower, especially at the edges of the stone panels of the Tower.
Travertine (Fig. 4) is used for protected exterior cladding around the outside, as well as for interior stone, on the plaza level of the Tower. The dominant colors of this variably colored stone are light brown and moderate reddish brown. This stone is Persian Red travertine, quarried near Azarshahr in East Azerbaijan Province, NW Iran (Price, 2007, p. 57). The stone is Quaternary in age (Javad M. Ghazi, 2015, personal commun.). This stone has been marketed under various other names, and some current websites erroneously note it as originating in Italy.
A variety of sedimentary structures can be found in the travertine. These include upward and outwardly branching brush, or shrublike forms, groups of vertical tubes formed by lithification around rising bubbles, and bacterial stromatolites, forms described in Chafetz and Folk (1984, p. 305-311). Rip-up clasts and vugs, some with dogtooth spar inside, are also present in the stone. Some of the cavities in the stone used here, as in many places where travertine is used, are filled with a matching cement. Although the exterior stone is protected by an extensive overhang, it is clearly more weathered than the same stone that is used inside the building.
Stop 2. One Charles Center (100 North Charles Street): Tinos Green marble (Greek Serpentinite)
One Charles Center, located on North Charles Street, just north of West Fayette Street, is a 23-story international-style office tower, mostly built of concrete, glass, and aluminum. The most striking aspect of this 1962 building from street level, however, is the use of a beautifully patterned green serpentinite (Fig. 5) at its plaza level. The stone is known commercially as Tinos Green marble (Dorsey and Dilts, 1997, p. 81) and also as Verde Tinos, and could generically be called a verde antique (antique green). This serpentinite is notable for its inclusion of prominent calcite veining (Price, 2007, p. 181), which forms reticulate patterns. The stone is quarried on the Island of Tinos, one of the larger of the Cycladic Islands, and is Jurassic in age. The panels are diamond matched, with panels placed so that their veining creates a diamond shape. Such polished panels, when used outdoors, are subject to surficial weathering, even where partly protected, as at this location. This stone was repolished in the 1990s, when the original design of the plaza was altered and original travertine paving was removed (Dorsey and Dilts, 1997, p. 81).
Stop 3. Basilica of the Assumption (409 Cathedral Street): Ellicott City Granite and Other Stones
The Basilica of the Assumption (Fig. 6) is located on Cathedral Street between West Franklin and West Mulberry Streets. It can always be viewed from the surrounding streets, but the gates that allow close access, as well as the interior, have restricted hours, which are posted on the Basilica’s website. Built between 1806 and 1821, this was the first great metropolitan cathedral constructed in the United States (Baltimore Basilica, 2014). Because this building once served as the first cathedral in Baltimore, it is also known as the old cathedral. When the Cathedral of Mary Our Queen (located about four miles to the north) was opened in 1959, the Basilica was designated as a co-cathedral. This building has been highly regarded as an early example of the neo-classical revival in ecclesiastical architecture (Howe, 2003, p. 141) and has been considered to be “Baltimore’s greatest work of architecture” (Dorsey and Dilts, 1997, p. 99). It was designed by the architect Benjamin Latrobe (1764-1820), who also designed the U.S. Capitol and other important buildings. Latrobe insisted on the use of stone vaulting for this neo-classical structure (Kennedy, 1982, p. 256). According to geologist E.B. Mathews (1898, p. 148), the Cathedral was also “one of the most important stone structures in the United States at the time of its construction.” Latrobe, a keen observer and a polymath, had an interest in geology. His publications include two articles on geological topics published in journals (Latrobe, 1799, 1809) and a lengthy published newspaper letter (reprinted in Latrobe, 1988, p. 251-255) discussing the origin of various stone types as well as his own efforts to utilize stone. Latrobe also would illustrate fossils and describe geologic sections (Hamlin, 1955, fig. 3; Latrobe, 1984, p. 107) with reasonable accuracy for the time. Thus, the “father of American architecture” was well grounded in geology.
Many sources (e.g., Mathews, 1898, p. 148; Maynard, 2002, p. 234) note that the Basilica is made of granite from Ellicott City, Maryland, a town located ~10 miles southwest of Baltimore. The stone, the Ellicott City Granite (also known as Ellicott City Granodiorite), was quarried either in Baltimore County or adjacent Howard County (Mathews, 1898, p. 148). The quantity of stone used for the building was a large amount for this time, especially since the extensive use of stone for architecture in Baltimore only began at the beginning of the nineteenth century (Maynard, 2002, p. 234). As has often been noted (by Maynard and others), the stone was hauled to the site in wagons pulled by nine teams of oxen. Stone transport using oxen was not unusual in America and Europe in the early nineteenth century, and even later. The large number of oxen used to transport the stone to Baltimore is similar to that used to transport heavy stone columns made of Cockeysville Marble (quarried just north of Baltimore) to the U.S. Capitol in the 1860s (Hazelton, 1897, p. 57), and more famously, Carrara Marble from the famous Carrara, Italy, quarries, high in the Apuan Alps to the harbor below (Società Editrice Apuana, 1996, p. 26-27, 115, 150-151).
The Ellicott City Granite is a complex, gneissic, and porphyritic feldspar-biotite granodiorite of Silurian age. Classically, the stone used for the cathedral has been considered a gneiss (Mathews, 1898, p. 148; Merrill 1891, p. 424). It is strikingly patterned due to the presence of large mafic enclaves and light-colored feldspar-rich intrusions. In general, this granite has held up well over time, especially in comparison to the more celebrated marble, serpentinite, and brownstone used for Baltimore structures in the nineteenth century. The stonework also held up well in the August 2013 earthquake, although plaster and brickwork did not fare as well and needed extensive repair. A small amount of granite from Colorado (rock unit not specified) was used to replace a window above the entrance during recent restoration, and that stone was painted to match the original stone (Robert Reier, 2015, personal commun.). Ellicott City Granite was also used for curbstones in Baltimore (Hawes et al., 1884, p. 282) and for many structures in Ellicott City itself.
Large, rectangular panels on the upper sides of the building are Aquia Creek sandstone, with the exception of the panel on the portico side, which is cast concrete (the original panel had been removed in the past to put in stained glass, which was subsequently removed and replaced with cast concrete during restoration between 2004 and 2006). Two smaller blocks of Aquia Creek sandstone were also used above the two front doors that flank the larger main front door of the Basilica. These were added in 1863-1864 when the portico was constructed. This stone is from the Lower Cretaceous Potomac Formation (or Group), quarried along Aquia Creek in Stafford County, Virginia. Latrobe was very familiar with this stone, and it was the topic of one of his journal articles (Latrobe, 1809). He also used this stone for the U.S. Capitol (Latrobe, 1984, p. 425-427). Latrobe referred to this sandstone as a “freestone,” that is, a stone that does not split preferentially when being worked. McGee and Woodruff (1992) have discussed the properties of this sandstone, and its weathering characteristics, in their report on its probable use for Baltimore’s Fort McHenry.
The portico (added to the building in 1863-1864) has a base and stairs made of a pale-pink biotite granite. Columns (Fig. 7) on the portico are a sandstone painted white to resemble white marble. Where the paint has chipped off, the stone can be seen to be fine grained and slightly arkosic. These columns are each composed of five sandstone drums (segments), 1.7 m (67.5 in) high, quarried from the Maritime Provinces of Canada. Cuyler (1951, p. ) notes that this stone is from Nova Scotia, but, according to Durkin (2007, p. 50), it is “New Brunswick freestone brought from Nova Scotia.” Robert Reier (2015, personal commun.) favors a New Brunswick origin for the stone. It is likely that the columns are made of Upper Carboniferous sandstone as that is what would have been available in these thicknesses in both provinces. Upper Carboniferous sandstone from the Wallace, Nova Scotia, area is one possible source (Parks, 1914, p. 71-77). It was known to have been exported to various cities on the eastern seaboard of the United States. But New Brunswick stone is known to have been used in New England (Martin, 1990, p. 39-41). To complicate the situation, the similarity of sandstone from Nova Scotia and New Brunswick, along with the earlier use of Nova Scotia stone in the United States, led to stone from both New Brunswick and Nova Scotia to be called Nova Scotia stone (Julien, 1884, p. 368; Merrill, 1891, p. 289). Whatever the exact source of the stone, it was obtained at an optimal time, as the 1854 Reciprocity Treaty was in effect, eliminating a previous duty on stone imported into the United States from Canada, and helping to initiate what Martin (1990, p. 38-39) has called a “golden age of sandstone” production in New Brunswick.
The portico is floored with white marble and gray limestone tiles (emulating the original stone flooring). Comparison of the gray tiles in different parts of the portico shows that they are weathering from a darker to a lighter gray color and that an interconnected network of tubular forms is becoming apparent in the stone in the process. These are probably trace fossils. The main doorway of the Basilica is white marble, and the two flanking doorways are pink Tennessee marble (Holston Formation limestone) painted to resemble white marble (the stone can be seen where the paint has worn away in places) (Fig. 8). The Holston Formation limestone contains abundant crinoid-column segments, each a single crystal, and bryozoans, as well as stylolites. This stone, quarried in eastern Tennessee, is Ordovician in age. The two flanking doorways were not original. Flooring inside the Basilica is white Yule Marble quarried in Marble, Colorado (McDonald, 2006). This marble formed during the Eocene/Oligocene due to contact metamorphism of the Mississippian Age Leadville Limestone. The interior of the Basilica contains a number of decorative stones used for the various smaller altars. Scagliola, a type of imitation marble produced by artisans who incorporated pigments into plaster mixed with animal glue (Cuyler, 1951, p. ), is used for the inset panels on the high altar (Durkin, 2007, p. 115).
Good examples of marble stone steps (Fig. 9) and brown-stone structures are located just across the street from the Basilica on West Mulberry Street. There are also examples of the once-common granite street pavers on North Sharp Street, just beyond these buildings.
Stop 4. Enoch Pratt Free Library (400 Cathedral Street): Salem Limestone (Indiana limestone), Cold Spring Dark Gray granite, Grand Tower Formation (Ste. Genevieve Golden Vein marble), and other stones; and Maryland State Library for the Blind and Physically Handicapped: Oneota Dolostone
The main building of the Enoch Pratt Library (Fig. 10) is located on Cathedral Street, between West Franklin and West Mulberry streets. The original part of the building was completed in 1933. The exterior of the Beaux-Arts style building is made of Salem Limestone (Indiana limestone), a widely used limestone from south-central Indiana. Limestone was chosen for this building as it was more economical than marble (Enoch Pratt Free Library Archives, 1928). It was probably the variety of Indiana limestone known as Standard buff (Lunn, 1930).The choice of Indiana limestone is fortunate, since the stone appears to hold up better to weathering in cities than does marble. The base of the exterior is a pink granite. Conway granite, Deer Isle Pink granite, or equivalents, were specified (Enoch Pratt Free Library, 2015, personal commun.). Conway granite would have been quarried in New Hampshire (Dale, 1923, p. 166), and Deer Isle Pink would have been quarried in the Deer Isle, Maine, area (recent quarrying has been on Crotch Island, offshore of Deer Isle; Busse and Hund, 1993, G-177). The main entrance is framed with carved Cold Spring Dark Gray granite (Enoch Pratt Free Library Archives, 1930) and sidewalk at the entranceway is travertine.
Panels of stone from the Devonian Grand Tower Formation in Missouri (Hinchey, 1946, p. 22) are located just inside the front entranceway. This gray- and gold-colored stone has been known commercially as Ste. Genevieve Golden Vein marble. Numerous large (up to 25 cm diameter) Middle Devonian colonial and solitary (Fig. 11) corals, as well as bryozoans, can be seen in the stone panels. Columns and wainscoting in the grand open interior of the main building are clad in pale yellowish brown to pale reddish brown Loredo Chiaro marble (Fig. 10), with mostly low trim of Pyrenees Black and White marble (McCauley and Wheeler, 1933, p. 388). The former, also known as Breccia Aurora marble or Breccia Aurora classica (as illustrated in Rossini [1987, p. 117]), is a coarsely brecciated limestone from Italy. It contains contorted and faulted layers, creating a variety of patterns, as well as small fossils. Many panels of this stone are book-matched so that adjoining panels appear as mirror images of each other. Pyrenees is a dusky yellowish-brown limestone quarried on the French side of the Pyrenees. A light-colored travertine is used for internal stairs.
The Maryland State Library for the Blind and Physically Handicapped is located directly behind the Enoch Pratt Free Library, at 415 Park Avenue. It is faced with Ordovician Oneota Dolostone from southern Minnesota. This is a dolomitic limestone sold under the name Kasota stone. The main side of the building faces west, taking advantage of the afternoon sun which casts a golden hue on this stone. (The Philadelphia Museum of Art takes similar advantage of this property of this stone.) Panels of Oneota Dolostone used here are 7.5 cm thick, especially appropriate as the stone is cut perpendicular to bedding so as to show the natural bedding of the stone. Since construction of this building in 1992, the stone has differentially weathered, with fossil burrows preferentially etching out. This can best be seen in windowsills (Fig. 12) and around the ventilation vent area on the West Franklin Street side of the building. Burrows are up to 3 cm in diameter, and when etched out, create tunnels into the stone. The preferential weathering is due to the difference between the calcareous burrows and surrounding, more dolomitic, rock matrix (Hannibal, 2014, p. 56).
Stop 5. Washington and Lafayette Monuments (North Charles Street and Mount Vernon Place): Cockeysville Marble
Construction of the Washington Monument, located in the heart of Mount Vernon Place, began in 1815; a lack of funds prevented its completion until 1829 (Mathews, 1898, p. 173). This monument was the first public monument erected in honor of George Washington (Mount Vernon Place Conservancy, 2015). Robert Mills, the monument’s architect, later designed the much larger and better-known Washington Monument in Washington, D.C. The Mount Vernon Place Conservancy restored the monument in 2014-2015. This included gentle cleaning of the exterior marble with water, use of D2, a detergent solution with proprietary chemicals (frequently used for cleaning gravestones) to remove stains in the marble, replacement of rusted iron cramps used to secure blocks of stone together with new stainless-steel cramps (the rusted cramps caused stone to spall in places, especially at the base of the monument), and various repairs to the stonework (Lance Humphries, 2015, personal commun.). Extensive work was also done in the interior of the monument.
The Washington Monument (Fig. 13) is constructed of Cockeysville Marble, obtained from sites north of Baltimore (Mathews, 1898, p. 173). The figure of Washington at its apex was carved from three blocks that were originally obtained as one piece more than 5.2 m (17 ft) long. According to Mathews (1898, p. 173), the block was from the Taylor quarry, located just west of the former railroad at Cockeysville. A contemporary newspaper article (Anonymous, 1829), however, stated that the block was “found in a field by itself’ on Mrs. Taylor’s farm. That account is essentially repeated in a commemorative book describing various aspects of the monument including ceremonies involved with the installation of its cornerstone and of the complexities of installing the Washington statue (Anonymous, 1849, p. 27), except that the book also notes that the stone, citing David Dale Owen, came from Mrs. Taylor’s “quarry.” Marble from the Scott quarries, located 8 km to the north of the Taylor quarry, was used for the Doric column and some other parts of the monument. And marble from the Charles Ridgely quarry was used for most of the base, although some parts including door surrounds and stairs may be from the Scott quarries (Lance Humphries, 2015, personal commun.). That stone, when closely examined, exhibits prominent veining (Mount Vernon Place Conservancy, 2015). The Cockeysville Marble is a fine- to coarse-grained crystalline marble of variable composition; both calcareous and dolomitic zones are present (Knopf and Jonas, 1929, p. 162), and the marbles used for this monument exhibit differences in the amount of accessory minerals and veining.
Weathering of the Washington Monument was apparent early on. One commenter (Anonymous, 1857) noted that the Washington monuments in both Baltimore and Washington were deteriorating after only ten years of exposure; in the case of the monument in Baltimore, this was an extreme statement. The monument has indeed weathered subsequently and the surface has been reduced. Resistant mineral grains are apparent at places, including on the Washington statue itself (seen on web close-ups and on the interactive display available in the lobby of the monument, and on the website of the Mount Vernon Place Conservancy, 2015). As part of the recent restoration work, a 3-D scan was made of this statue, and measurements were taken from the scan of projecting resistant minerals (identified as tremolite) of the statue (Lance Humphries, 2015, personal commun.). Projecting areas were 2.0 mm below the left iris, 3.2 mm above the iris, and 2.5 mm from the tip of the nose of the statue. An average of 11 measurements on the top and sides of the north stairway support at the base of the monument (taken by us using a micrometer in August of 2015) showed projecting areas consisting of resistant minerals to be an average of 1.8 mm higher than the surrounding marble. This is slightly more than that of projecting material in the Battle Monument bollard (Stop 10), and greater than that of similar material at City Hall (Stop 9).
Coarse-grained white marble balusters were installed close to the monument as part of a redesign of the Mount Vernon square in 1917 (Fig. 14). The balusters were originally made of Cockeysville Marble from the Beaver Dam Quarry (Fig. 1), but some subsequent replacement balusters were made of marble from Georgia (Lance Humphries, 2015, personal commun.). This coarse grained marble, known commercially as Georgia marble and other names, is the Cambrian-Early Ordovician Murphy Marble quarried in the Tate area, northern Georgia. The balusters show a relatively rapid degree of weathering, especially compared to the railing they support. This is typical of marble balusters made of coarse grained marble (Doe, 1989, p. 5; Hannibal and Schmidt, 1994, p. 11) in urban environments.
With a reservation, it is possible to climb the 227 marble steps to the top of the tower. The way is now lit by electric lights, but those who climbed the tower after it first opened to the public in the 1800s carried lanterns to light their way. Replacement metal cramps used to firmly attach adjacent blocks of the marble on the low wall directly outside can be seen from the viewing windows. Several other stone structures are visible from the doorway views, notably the top of the Mount Vernon Place United Methodist Church (Stop 6) to the north and east, the tall spire of the First and Franklin Presbyterian Church, made of New Jersey brownstone, seen to the northwest, and the Baltimore City Jail complex, with its Romanesque 1859 core made of Baltimore Gneiss from Jones Falls, Maryland, to the northeast.
The Lafayette Monument (Fig. 15), located close to the Washington Monument, was erected in 1924. It consists of a bronze statue mounted on a marble base. The bronze statue has been coated with wax for protection, and so is neither a bronze color nor does it have the familiar green patina of weathered bronze. Dissolved material from the statue has stained the marble somewhat (this is typically due to copper used in bronze).
Use of bronze for the statue contrasts with the use of marble for the statue of Washington. Bronze would not have been readily available at the time that the Washington monument was installed. The first large bronze statue cast in the United States was the Andrew Jackson statue near the White House, cast in 1853 (Carol Grissom, 2015, personal commun.). The use of bronze for the Lafayette statue may, at least in part, be due to the realization that marble weathers over time. Benjamin Latrobe, in an 1800 letter concerning a monument to George Washington (Latrobe, 1984, p. 162), noted his displeasure with bronze statuary as well as stone statuary, the former because of its lifeless appearance and the latter because parts could be so easily broken from it. The latter comment is applicable to the Washington Monument, and especially, the Battle Monument (Stop 10).
The Peabody Library, clad with Cockeysville Marble, is located just southeast of the Monument. Flooring of the entranceway includes a number of stones that are similar to those used in City Hall (Stop 9).
Stop 6. Mount Vernon Place United Methodist Church (North Charles Street and Mount Vernon Place): Serpentinite and Sandstones
This neo-Gothic style church (Fig. 16), located at the corner of Mount Vernon Place and North Charles Street near the Washington Monument, was completed in 1872. Designed by Thomas Dixon and Charles Carson, the Mount Vernon Place United Methodist Church has been celebrated both for its Gothic details and its polychromatic exterior (Hayward and Shivers, 2004, p. 200). Its striking coloration is due to the contrast of its serpentinite exterior with its sandstone trim (Fig. 17).
This stone has been badly weathered, as is the case of similar serpentinite churches and other structures in West Chester, Pennsylvania (Stone, 1932, p. 105), Philadelphia (Brown, 2003; Meierding, 2005), Pullman, Illinois (now part of Chicago), and Cleveland, Ohio (Hannibal, 1999, p. 51). The propensity of this rock to weather was already becoming apparent by 1884 (Hawes et al., 1884, p. 29), as astute observers noted the disfiguration of polished slabs of this stone exposed to the urban atmosphere. Serpentinite’s apparent susceptibility to urban pollutants was also noted by the Pennsylvania Survey early in the twentieth century (Brown and Ehrenfeld, 1913, p. 124-125). The relatively restricted usage of serpentinite in cities in the eastern United States suggests that the propensity of serpentinite structures to spall was widely recognized early in the twentieth century, at least by ecclesiastical architects. More recently, Meierding (2005) has related the weathering of exposed serpentinite in Philadelphia to acid precipitation, and others (e.g., Pereira et al., 2007) have warned about the inappropriate usage of serpentinite. A large restoration project in the 1930s included the replacement of thousands of blocks of stone for the Mount Vernon Place United Methodist Church. Spalling has continued, however, with pieces of stone falling off the building over time (Parish, 1971). The difference between the original stone and subsequent replacement stone is easy to discern: the newer stone is darker green in coloration, the more weathered stone has a lighter, yellower coloration. This difference is also clearly seen where the more weathered stone is exfoliating, exposing darker stone beneath. At least some of the serpentinite was quarried in Maryland (Parish, 1971), perhaps the Bare Hills area of Baltimore County, part of the Soldiers Delight Ultramafic Complex. Much, or even most, of the stone used for the church may, however, be serpentinite from the well-known Brinton Quarry in Chester County, Pennsylvania: Mount Vernon Place United Methodist Church may be the unidentified church in Baltimore mentioned by Hawes et al. (1884, p. 177) as being made of a small amount of stone quarried near Baltimore and a greater amount of stone from the Brinton Quarry. Both the Pennsylvania and Maryland quarries are part of a large serpentinite area that stretches across the state boundary (Bowles, 1939, p. 205). Production of serpentinite blocks from Maryland quarries was also limited when the church was constructed (Mathews, 1898, p. 193-194). The serpentinites from both sites are similar as far as color and weathering characteristics.
Two types of sandstone (Figs. 17–18) are used for trim: a reddish brownstone and a light-colored quartzose sandstone. Both of these have taken on a darker patina over time, so the true color of these stones can only be seen where there has been some deterioration or where parts have broken off. Overall, the building has in part experienced a color reversal, as the sandstones have darkened and the serpentinite has lightened. This is a typical pattern seen in other serpentinite buildings in other cities with sandstone trim (Hannibal, 1999, p. 15).
The brownstone is medium-grained, arkosic, and highly micaceous. The other, light-colored fine-grained quartzose sandstone has small ferruginous spots of iron cement. Its characteristics are consistent with the Berea Sandstone, a Devonian sandstone quarried in northeastern Ohio (Hannibal et al., 2006, p. 204), and which is known to have been used in Baltimore (Hawes et al., 1884, p. p. 282). This formerly lighter-colored sandstone has also acquired a darker patina (typical of the Berea Sandstone) than the reddish brownstone, reversing and greatly diminishing the alternating two-toned light-and-dark color-banding scheme of the large relieving arches (Fig. 17), window frames, and other features.
The two sandstones have also differentially weathered; this is apparent at the pier buttresses, where offsets made of brown-stone have spalled badly whereas the other sandstone has proved more resistant (Fig. 18). There are a number of other sites where brownstone has weathered badly in downtown Baltimore. These include the 1852 Grace and St. Peters Church on West Monument Street and Park Avenue, which is made of Triassic Connecticut brownstone. That brownstone is similar to, but slightly coarser than, the brownstone of Mount Vernon Place United Methodist. The base of the church and the stairs are granite as are columns flanking the front doorways.
Stop 7. War Memorial Building (101 North Gay Street): Salem Limestone, Red Ark Fossil marble, and Other Stones
Baltimore’s War Memorial Building is located on North Gay Street between East Lexington Street and East Fayette Street. The building, designed by Laurence Hall Fowler and originally dedicated in 1925 in honor of veterans of the First World War, is a large classical-style building, essentially a “modified Greek Revival temple” (Hayward and Shivers, 2004, p. 249). Because of its prominence and its use of large amounts of stone, this building was featured in the June 1925 issue of Through the Ages (Anonymous, 1925b). The stones used include several quarried in the Midwest. These include three Mississippian-age limestones known in the building trade as Indiana limestone (Salem Limestone), Red Ark Fossil marble, and Napoleon Gray marble. Indiana limestone was especially popular at the time that the War Memorial was being built. At the War Memorial Building it is used for exterior cladding and surrounding walls and for the two large sculptures of marine horses (Fig. 19) by Edmund R. Amateis (1897-1981) that flank the front of the structure (Kelly, 2011, p. 95). These sculptures were Amateis’s first important large commission (Gurney, 1985, p. 256). He subsequently did other large sculptural works, notably for the Federal Triangle in Washington, D.C. (Gurney, 1985, p. 242, 252), a project that utilized a large amount of Salem Limestone, and which also featured a number of horses in its sculptural program. Salem Limestone that is used here, like that used elsewhere for building stone, is a grain-supported, calcitic limestone composed of small fossils and fragments of larger fossils. The most apparent are circular sections of crinoids (and/or blastoids) and fragments of bryozoans. These fossils can be most easily seen in the horse statues. Ichnofossils (trace fossils) can also be observed in the stone used for the walls around the building. These include large examples of the elongate, annulated form known as Eione or Margaritichnus (Fig. 20) typical of the shoal facies of the Salem (Archer and Brown, 1990, p. 24). The stone slabs seen here containing these fossils are placed so that originally horizontal surfaces are seen vertically. This ichnofossil has been interpreted as being formed from rounded pellets of sediment excreted by wormlike animals (Häntzchel, 1975, p.W82), but Seilacher (2007, p. 52) has more recently classified Margaritichnus as an arthropod tunnel. Smaller sinuous ichnofossils, either Helminthopsis or smaller Eione/Margaritichnus, are also seen in the stone. Crossbedding can also be observed in places. The steps leading up to the front of the War Memorial are granite.
The most prominent stones used inside the most accessible part of the building, the exhibit room on ground level, are two Mississippian limestones from Arkansas and Missouri. A limestone known as Red Ark Fossil marble clads the bottom 1 m of the 20 Ionic columns in the main exhibit room, as well as wainscoting in various parts of the interior of the building (Fig. 21), and is also used for internal doorways. Red Ark Fossil marble belongs to the Mississippian Boone Formation and was quarried in Cartney, Arkansas. Its color here varies from a moderate brown to a very dark red to a blackish red. The most common fossils found in the stone are crinoids and possibly blastoids. Light-colored crinoid (and/or blastoid) columnal segments contrast with the colored matrix. Concentrations of segments (Fig. 22) may indicate the disarticulated remains of individual crinoids. Red Ark Fossil marble is most famously used for the cenotaph of Abraham Lincoln. Flooring is Napoleon Gray marble, a Mississippian limestone quarried in Phenix, Missouri, from the undivided Burlington-Keokuk Limestones (Hannibal and Evans, 2010). It is light olive gray in color, and contains fossils of brachiopods (Fig. 23), rugose corals, and crinoids. Dark-colored stylolites (Fig. 23; known as crowfoot in the quarry industry, and as veining in the marble industry) are prominent features of this stone. Some of the stylolites seen here cut through fossils, and there has been some dissolution along some of the stylolites. Travertine, Belgian Black marble (a black limestone), and Rose Tavernelle marble (a light-colored limestone) are also used inside this building (Anonymous, 1925b; Hilgartner Marble, 1925) on the upper level which is not typically open to the public. Belgian Black marble is a Devonian/Mississippian limestone quarried in Belgium (Groessens, 1987); Rose Tavernelle is probably from Vicenza, Italy. Some small panels of Baltic Brown granite, a rapakivi granite (note the large zoned feldspar crystals) quarried in Finland, have been placed near the doorways in more recent times, probably in response to weathering of the original stone.
Stop 8. Baltimore Police Headquarters (601 East Fayette Street): Morton Gneiss (Rainbow granite)
Baltimore Police Headquarters (Fig. 24) is located on East Fayette Street south of its intersection with North Frederick Street. The building is clad in Rainbow granite (Fig. 25), one of the commercial names for Morton Gneiss, a rock unit quarried in Minnesota by the Cold Spring Granite Company. This coarsely crystalline migmatitic gneiss (Wooden et al., 1980) is found in a number of exposures in several locations in the Minnesota River Valley in south-central Minnesota, and is Archean (3.5 billion years old) (Bickford et al., 2006, p. 102), ranking it among the oldest building stones in use. Morton Gneiss is typically used on the ground level of buildings; it is more resistant to urban pollutants than limestone or sandstone (Williams, 2009, p. 72). Initially, basalt (likely formed at a spreading center) underwent partial melting during subduction (~700-800 °C), resulting in a stone with basalt rafts in it. Continental collisions at 2.6 billion years ago resulted in an infusion of felsic magma that infused the Morton Gneiss with its pink coloration. Partial melting and compression resulted in the swirling patterns characteristic of this rock. The stone displays light gray tonalitic (mainly feldspar and quartz) gneiss layers and pink granite gneiss layers, that are intruded by dark layers and enclaves of amphibolite (Fig. 25).
Stop 9. Baltimore City Hall (100 Holliday Street): Cockeysville Marble and Other Stones
Baltimore’s ornate City Hall, located on Holliday Street between East Lexington and East Fayette Streets, was completed in 1875 using Renaissance and French Second Empire architectural elements (Fig. 26). The exterior is Cockeysville Marble, brought to the site by means of a special railway line by Hugh Sisson, who supplied the marble (Hayward and Shivers, 2004, p. 188), likely from the Beaver Dam quarry. This method was far more efficient than the teams of oxen used in transporting stone to the Basilica of the Assumption (Stop 3) earlier in the century. The marble used for City Hall is rich in phlogopite mica and in pyrite. Many years ago, Bowles (1939, p. 205) noted that pyrite in the Cockeysville Marble “is unusually stable, as evidenced by marble structures containing pyrite being exposed to the weather for over 100 years without any evidence of staining.” Although there have been exceptions (Mathews, 1898, p. 178), the pyrite seen in this building appears to be stable. This may be due to the buffering effect of the marble itself (Page Herbert, 2014, personal commun.). The marble, however, has weathered over time as one might expect due to acid precipitation. Based on a sampling of sites on the east and south sides of the building (measured by us with a micrometer in 2015), resistant areas project on average 1.3 mm from the surface. As would be expected because of its later date, this is less than that of the older Battle Monument (Stop 10) and the Washington Monument (Stop 5). A greater amount of degradation of the stone can be observed in places, such as on that and near the columns on the west (Guilford Avenue) side of City Hall (Fig. 27). Here it is apparent that lower parts of the columns have deteriorated. Serious problems due to stone deterioration of City Hall have been evident for some time (Linskey, 2009), and some of these have been ameliorated, in part by replacement of some stone. The original marble has also yellowed over time as can be seen by comparing the color of less-weathered replacement stone with the original stone. McGee (1989, 1996, 1999) emphasized the role of acid rain in stone degradation, whereas Mossotti et al. (2001) found a strong relationship between rain-delivery conditions and the shape and orientation of objects that were weathered. Other regional comparative studies (e.g., Meierding, 1993; Bauer et al., 2002) of marble weathering have noted a relationship between pollution sources and degree of marble degradation.
Despite this, tooling of the large marble blocks (Fig. 28) is still evident. These blocks have a finely bush-hammered interior (a treatment with a bush hammer, which has a rectangular head with sets of protruding points), surrounded by a chisel-drafted margin.
The sidewalk on the east side of the building is a greenish-gray to brownish-gray bluestone. Such stones have been classically quarried in New York and Pennsylvania, particularly for use in flagging (Bowles, 1939, p. 97-99), as these well-indurated sandstones provide a relatively nonslippery surface. It is likely that the stone here is Devonian in age (Dickinson, 1903).
The interior of City Hall, which may be visited by appointment, contains a multi-story rotunda. The eight Doric columns on the first floor of the Rotunda are made of pink Holston Formation limestone (Tennessee marble). Dark stylolites and light-colored crinoid segments are readily apparent in the columns. Surrounding pilasters are scagliola (faux stone). The floor is composed of various stones, including a white marble, a black limestone with light-colored crinoid pieces, and a mottled red-and-white marble, probably Jasper marble, a quartzose dolomite (Dale, 1912, p. 43) from Swanton, Vermont. The inset design in the center of the Rotunda floor (Fig. 29) is composed of white marble, yellow Sienna marble (a slightly metamorphosed Jurassic limestone quarried in Italy) and a black limestone. An original building plaque on the wall consists of a black limestone panel containing crinoid columnals and a frame of Holston Formation limestone replete with bryozoans. More black limestone, marble, and scagliola are used throughout the original part of the building.
Stop 10. Battle Monument (Battle Monument Park,185 East Fayette Street): Cockeysville Marble
The 39-ft-high Battle Monument (Fig. 30) is located in a small park in the middle of North Calvert Street, near its intersection with East Fayette Street. The Monument, designed by the French architect Maximilien Godefroy and dedicated in 1827, commemorates the Americans killed during the defense of Baltimore during the War of 1812 (Hayward and Shivers, 2004, p. 80-81). Soon after the erection of this monument it was selected as the symbol of the City of Baltimore, and it remains on the city seal today. The lower parts of the structure, notably the Egyptian-revival base, is made of Cockeysville Marble; the upper parts are imported stone (Fig. 31). The original statue of a woman at the top (known as Lady Baltimore), a statue of an eagle next to her, and the carved griffins on the corners of the top of the base (Fig. 32), were carved from Italian statuary marble by Italian sculptor Antonio Capellano (1780-1840) (Scharf, 1881, p. 269; Hunter, 1959, p. 3). The term Italian marble, especially when used in reference to statuary-grade marble as Capellano (in Fairman, 1927, p. 37) used the term, was, in the nineteenth century, a virtual synonym for Carrara Marble, a Jurassic-age marble quarried in Italy’s Apuan Alps. The statue that now tops the monument is a re-creation installed in 2013; the features have been somewhat restored, including an extensive facial reconstruction. The original, highly weathered, statue is now exhibited on the second-floor landing of the Maryland Historical Society Museum and Library (Walker, 2013), located at 201 West Monument Street. The original statue is severely weathered, and the main stone used is free of the phlogopite mica veins typical of much of the Cockeysville marble. The removal of the statue from its historic context was done to prevent further deterioration. Such drastic measures are not unknown elsewhere. The original marble statue of Oliver Hazard Perry, part of an Ohio monument commemorating another aspect of the War of 1812, is now preserved inside a building at the Perry Victory and International Peace Memorial (Hannibal, 2011). And Michelangelo’s David, made of Carrara Marble, is now famously preserved in the Academy Gallery in Florence. It appears that Julien (1884, p. 366) was correct in his observation that “Italian marble has been found to be incompetent to withstand the severity of our climate, when used for outdoor work.” He also (p. 323) noted that statuary marble from Rutland, Vermont, was “best fitted for use when it is not exposed to the weather.”
Parts of the original Lady Baltimore statue had been repaired in the past; one hand and the associated rudder has been replaced by reusing marble that had been used for steps in Baltimore (Kelly, 2011, p. 83), which was probably the Cockeysville Marble. The re-created statue is made of concrete and has a roughened surface replicating the highly weathered surface of the original. Molds were also made of the griffins so that they could be more easily replicated in the future.
The effects of weathering on the remaining original parts of the monument are clearly severe after 200 years. Cracks course through much of the marble column and base, and carved inscriptions are no longer crisp. It is likely that all the marble surfaces have been reduced to some extent. This surficial reduction is very apparent on the marble bollards (Fig. 33) by the monument. Based on a series of 25 measurements (by us using a micrometer in 2015) of the height of the now-protruding, resistant grains in an east bollard, as well as a series of 14 measurements of a north bollard, this reduction is an average of 1.7 mm, but one measurement of the height of resistant grains on a SW bollard was 2.9 mm.
The marbles apparently held up well into the late 1800s: Hawes et al. (1884, p. 282) noted that the lettering on the cornerstone of the monument “remains quite distinct, showing that this material, even when not selected with any care, stands the test of time quite well.” Mathews (1898, p. 185) made a similar claim for lettering on tombstones made of Cockeysville Marble going back to 1829. Therefore, it appears that weathering was either relatively minor until the turn of the century, or weathering accelerated at that time due to greater atmospheric pollution. The doors of the monument base are made of single slabs of a dark-gray stone.
Tidal Gray granite from Elberton, Georgia, is used for the low walls and seats on the north side of the monument (McCann-Murray, 2001, p. 12). This gneissic granite is Proterozoic in age.
Stop 11. Mercantile Trust and Deposit Company (222 East Redwood Street): Brownstone
Located at the northeast corner of Calvert and Redwood Streets, this dark red, Romanesque Revival building was designed by Wyatt and Sperry and constructed in 1885-1886 of brick and stone (Hayward and Shivers, 2004, p. 212). It is currently the home of the Chesapeake Shakespeare Theatre. Built like a fortress with double walls and iron window grates, the Mercantile Building survived Baltimore’s Great Fire of 1904. It is listed in the National Register of Historic Places. Although most of the building’s exterior is made of brick, there is extensive trim made of brownstone (Fig. 34). The stone has been variously referred to as a light red freestone (Hunter, 1960, p. 4), local stone (Kelly, 1993), or Seneca Red sandstone (McCann-Murray, 2001). Lower courses of stone (referred to as a “water table” in architectural vocabulary) are composed of fine-to-very-fine grained sandstone that is exfoliating. The upper sandstone is slightly coarser, fine-to-medium grained sandstone and is somewhat darker in color.
Seneca Red sandstone, the most important and most used sandstone quarried in Maryland (Mathews, 1898, p. 199), is from the upper Triassic Poolesville Member of the Manassas Sandstone. It consists of a brownish-red arkosic sandstone with red siltstone (Southworth et al., 2007). Seneca Red sandstone is found in the Culpeper Basin, one of several Triassic sedimentary rift basins that are distributed from eastern Canada to North Carolina. The stone was quarried in both Montgomery and Frederick County, Maryland, along the Potomac River, ~20 miles upstream from Washington, D.C. Chief minerals in this rock are quartz, microcline and plagioclase feldspar, and muscovite; the primary cementing agent is ferruginous cement (Mathews, 1898, p. 203). The red color is largely due to iron oxide in the rock, mainly in the cementing material. Since construction of the Mercantile Trust and Deposit Company building, weathering has had an effect on the building stone used for this building, but not to the extent of that of a number of other brownstone buildings in Baltimore. Seneca Red sandstone was a popular building stone in Baltimore and Washington, D.C., due to its accessibility and ease of transport. The sandstone was also popular because it was easy to cut and carve for decorative stone when first quarried, but then hardened over time. It has the additional quality of changing color over time, such that initially the quarried stone was a lilac gray, and gradually weathered to a dark red with exposure to the air. Seneca Red sandstone was used in the building of the original Smithsonian Institution building (the “castle”) in Washington, D.C., constructed between 1847 and 1855) (Mathews, 1898, p. 200; Livingston et al., 2015). Comparison of exfoliated pieces of the lower course of stones of the Mercantile Deposit and Trust Building to stone exposed at the Seneca Red Sandstone quarry at the mouth of Seneca Creek in Montgomery County supports the interpretation that the brownstone is Seneca Red sandstone. However, this is in need of further study.
An interesting architectural design for the time was the placement of “spy steps” (Hunter, 1960, p. 7; Dorsey and Dilts, 1981) into two sides of the bank building. This would allow night watchmen, and police, to step up and peer into the bank while on patrol (Arnett, 1969; Fig. 35). A brass ring at shoulder level was used help them to balance on the step.
Stop 12. The Gallery (200 East Pratt Street): Taivasalo granite and European Limestones
The exterior of The Gallery (Fig. 36), an indoor shopping mall-hotel-office tower complex across the street from the Inner Harbor, which opened in 1986, is faced with Taivassalo granite (Fig. 37) from Finland. This is a red granite that has been widely used in North America and Europe. It has commonly been used for cladding of large buildings and other structures, including the similarly named Galleria shopping mall in Cleveland, Ohio (Hannibal and Schmidt, 1994, p. 18). This granite is Proterozoic, ~1.6 billion years old, part of the Vehmaa rapakivi batholith of SW Finland (Lindberg and Bergman, 1993). Confusingly, the name Balmoral Red granite has also been applied to this stone, especially, but not only, in the past.
Tiles on the floors on the shopping area of The Gallery are limestone. Most are a grayish orange pink limestone (either Hauteville marble, or a similar limestone quarried in central France). It contains a variety of Mesozoic marine fossils, including high- and medium-spired snails seen in both longitudinal and cross-section, rudistids, corals, pelecypods, and foraminiferans.
These include high-spired snails (Fig. 38) belonging to the Jurassic-Cretaceous family Nerineidae, which are notable for their elaborate internal folds (Steffen Kiel, 2015, personal commun.). There are also abundant burrow systems and complex oncolites. The dark gray inserts in the floor are generally similar to Nero Marquina marble, a dark middle Cretaceous limestone quarried in central Spain (Fiori et al., 1998, p. 260-261), but are pinkish in many places.
Tom Doyle (Hilgartner Natural Stone Company, Baltimore) provided information on stone used at several stops, Jeffrey Mathews, Trade International, supplied information on hard-to-identify stone, and Lance Humphries, chair of the Restoration Committee, Mount Vernon Place Conservancy, provided information on the restoration of the Washington Monument. Joan Wolk and Michael Johnson, Enoch Pratt Free Library, provided information on stone used for the library, Robert Reier supplied information on stone used for the Basilica of the Assumption, Steffen Kiel, University Göttingen, identified the fossil snail figured, and Javad M. Ghazi provided information on the age of Persian Red travertine. Jeanne Davis, curator, Office of the Mayor, Baltimore, facilitated examination of the interior of City Hall. Page Herbert discussed marble properties with us. Peggy Perazzo’s website (2015), Stone Quarries and Beyond, was also utilized as part of this study. Wendy Wasman, Cleveland Museum of Natural History, assisted with references, and University Circle Future Connections students Jarrett Gorecki and James Wright helped compile the table and check references. Kathleen Farago, Cleveland Heights-University Heights Library, read and corrected manuscripts of this study. This chapter was reviewed by Carol A. Grissom, Smithsonian Museum Conservation Institute, and Michael Sandy, University of Dayton.
Figures & Tables
Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015
Prepared in conjunction with the 2015 GSA Annual Meeting in Baltimore, Maryland, this volume contains guides to field trips in this historic region. Emanating from the Fall Line city of Baltimore, these trips reflect the diversity of geological features in the mid-Atlantic region including the Piedmont, Appalachian Mountains, and Coastal Plain, and the importance of geology on the development and construction of the Baltimore-Washington, D.C., metropolitan area. Trips to the core of the Appalachian orogen concern themselves with the tectonic and metamorphic history, early Paleozoic carbonate platform development, Devonian paleoclimate, and coal-mine fire hazards. Excursions to the Coastal Plain examine various aspects of Cenozoic stratigraphy, structure, barrier island formation, and wetland and ecosystem development. A variety of trips also explore urban geology, including building and monument stones of Baltimore and Washington, D.C., urban hydrogeology, and Civil War battlefield geology.