Abstract Building stone is a significant product in most human communities. While some civilizations paid more attention to the aesthetics of the stone, others focused more on physical properties, especially durability, as well as the ease of transportation to construction sites. These latter issues determined which rocks were exploited, in preference to others, for centuries. Ancient Roman society became expert in constructing durable engineering projects (e.g. roads, bridges and aqueducts). Most of their projects were realized using local granites and most remain in excellent condition today. The historic cores of many European cities need to preserve their integrity, using the original building stone of the city both for new construction and for restoration. A supply of the original material should be preserved in order to avoid use of alternative building stones when restoring old monuments. In Salamanca, a specific unique granite was used to build many of its monuments that are now preserved as part of the UNESCO World Heritage Site. An attempt to preserve this architecture and restore it, when needed, with the original material is the main focus of our paper, as some experiences using other types of rocks have led to unfortunate results.

Abstract Reims Cathedral is a major monument in the NE of France originally built with local Lutetian limestone. The recent closure of the last quarries has made restoration using the same stone more complicated. The restoration stones used currently are Lutetian limestones from the centre of the Paris Basin (Saint-Pierre-Aigle and Saint-Maximin stones). Mapping of the Cathedral's façades confirmed the data from ancient manuscripts: Courville stone was the original building stone, but several other local stones from various quarries and beds were also used. As a follow-up to this mapping, Lutetian limestones from five disused quarries were sampled for petrophysical characterization tests: thin section analyses, porosimetry, capillary and drying kinetics. The petrophysical properties of the limestones showed differences between the two main local stone types ( Ditrupa limestone and miliolids limestone) and also between the quarries. This study addresses the difficulty of selecting new stone for restoration. Should ancient quarries be re-opened? If so, which ones?

Abstract The Lede stone (Lutetian, Eocene) is an important historic building stone used in the NW of Belgium. In Ghent, it is dominant in the post-Romanesque built cultural heritage. Its use was restricted several times by socio-economic constraints. Since quarrying and production started to cease from the seventeenth century, periodic revivals favoured the use of Lede stone for new buildings and restoration projects. Sulphation is the main threat for the Lede stone as black crusts are the most common degradation phenomena on this arenaceous limestone. Around the turn of the nineteenth century, the Belgian Gobertange stone was the most widely used replacement material. Throughout the twentieth century, the use of replacement material shifted towards French limestones. However, their colour, texture and petrophysical properties differ from the Lede stone, for which a natural yellow–brown patina is very characteristic. In order to solve this mainly aesthetic issue, several new stone types are used as replacement stone in the twenty-first century, while many others have been suggested. It remains, however, difficult to find a replacement stone that matches the visual and petrophysical properties of the Lede stone. One remaining Lede stone quarry pit has increased its activity since 2011, offering the opportunity to use new Lede stone as replacement stone.

Abstract Conservation of the built heritage requires knowledge of the characteristics and use of the constituent materials and their state of conservation. Knowledge of the material's source is important for laboratory studies and stone replacement, but it also has historic-cultural significance with respect to the exploitation of stone resources in the past. In this sense, we present a study of ‘Pietra Gentile’, a traditional building material of southern Italy, through which we aimed to acquire knowledge concerning the quarries, characteristics of extracted materials, use and decay features within buildings. Ancient and active quarries were identified and the petrographical, chemical-mineralogical and physical features of the quarry materials were studied. The use of the stone was documented in many historic towns in the area, including monuments and minor buildings, and the main decay morphologies were detected by field activities and laboratory analyses. The high susceptibility of the stone to the actions of water and salts was highlighted. Field and laboratory data of quarries and artefacts were organized into a database as a source of knowledge useful for the evaluation, preservation and promotion of cultural heritage.

Abstract The paper presents an overview of the principal stone materials used in the historical architecture of Tuscany, a region of central Italy characterized by a great variety of landscapes. The large number of these materials reflects the complex geology of the region, where each village and town has a unique identity conferred by the architecture and typical colours of the construction materials. The urban areas that have developed in the foothills of the Apennines are, characterized by the use of sandstone, while the towns and villages of central-southern Tuscany are generally more heterogeneous, with an abundant use of bricks and travertine. The information presented is focused on the use of the stone materials during the different epochs, their geopetrographical characteristics and their most common durability problems.

Abstract Arising mainly from its exceptionally varied suites of igneous and sedimentary rocks, Cornwall has a rich variety of building and decorative stones that were extensively exploited, both for local use and for export, before concrete and brick came to dominate construction in the twentieth century. Many of the types of building stone, such as elvan and sandrock, do not occur outside Cornwall, so local stone provides much character to the local built environment. Granites were extensively worked in the eastern part of the Carnmenellis Granite (mainly in Mabe parish), in the St Austell Granite (Luxulyan, Carn Grey and the china stone areas) and on Bodmin Moor (De Lank, Hantergantick, Cheesewring, etc.), as well as in the Kit Hill, Tregonning and Land's End granite masses. The predominant type used was the ‘coarse grained megacrystic biotite granite – smaller megacryst variant’ of Hawkes & Dangerfield. A significant trade in granite developed in the nineteenth and early twentieth centuries, employing large numbers of skilled quarrymen. Finished granite was exported all over the world; many iconic buildings in London and other major cities use Cornish granite. A tourmalinized granite, luxullianite, was an important decorative stone, and was used for the Duke of Wellington's sarcophagus in St Paul's Cathedral. Schorl rock is often found in older buildings in the granite areas. Most pre-nineteenth century granite building did not use quarried stone but used ‘moorstone’ obtained from boulders lying on the surface of the granite uplands. Large quantities of ‘minestone’ have been used in vernacular buildings, past and present, and in some medieval churches, sourced from the waste tips of metalliferous (both alluvial and vein operations) and china clay workings. Allied to the granites are the fine-grained elvans of granitic composition, usually intruded in the form of dykes. Greisening often improves the durability of elvans, which have been extensively used in some of the finest stone buildings in Cornwall, such as St Austell church tower, Antony House (NT), Trelowarren, Place (Fowey) and the Georgian buildings of Lemon Street, Truro. The best-known elvan quarries were at Pentewan, which yielded a freestone capable of fine carving. However, not all buildings described by architectural historians as being of Pentewan Stone came from Pentewan. Another important elvan was Newham Stone, widely used in the older buildings in Truro. Tremore elvan was used, together with luxullianite, mainly as a polished decorative stone to line Porphyry Hall at Place in Fowey and in other high-status buildings. Basic igneous rocks include an Upper Devonian metadolerite at Cataclews Point, west of Padstow, which provided the extremely durable Cataclews Stone, used from medieval times onwards for fonts and church carvings in the area around the Camel estuary. A more unusual stone, produced by carbonatization of an ultrabasic intrusion, is Polyphant Stone, mainly used for interior use and by sculptors, composed of a mixture of talc, chlorite, and various calcium and magnesium carbonates. The Polyphant Quarry was recently reopened to supply stone for the rebuilding of Newquay parish church and to supply stone for sculpting. Allied to Polyphant Stone is Duporth Stone, obtained from the cliffs of Duporth Bay, south of St Austell, which was used in the pillars of Truro Cathedral. Basic hyaloclastite was the main stone used in the great Norman Church of St German's in SE Cornwall. The Lizard ophiolite complex provided a source of serpentine for building and for the manufacture of polished slabs; ornaments made from serpentine are still produced. Slaty mudstones and sandstones of Devonian and Carboniferous age have been extensively used for traditional buildings throughout Cornwall, nowadays much slaty mudstone is still used for building and for Cornish hedge building. The Upper Devonian Delabole Slate Quarry has yielded high-quality roofing slate from Tudor times onwards but there are many other large active and disused roofing slate quarries in the Tintagel area and elsewhere in Cornwall, such as the underground slate workings at Carnglaze, now a tourist attraction and concert venue. Devonian sandstones, usually of turbiditic origin, are widely used for vernacular building in south Cornwall, and Upper Carboniferous turbidite sandstones are used in north Cornwall. The geologically youngest building stone, seen in the Newquay and Padstow areas, is a cemented bioclastic Quaternary beach sand, laid down at a time of high sea level during an interglacial as a raised beach. It is known locally as ‘sandrock’ but is a relatively weak building stone. St Carantoc's Church at Crantock and St Piran's Church on Perran sands were largely built of it. Supplementary material: A more detailed review of the various granite and elvan quarries that have been worked in Cornwall is available at http://www.geolsoc.org.uk/SUP18675 .

Abstract A large number of different building stones were used during the period AD 950–1850 in West Sussex churches, with 52 different types identified and named in this study. The building stones include local Tertiary and Cretaceous rocks, as well as imported rocks from the Isle of Wight, Dorset and Normandy. One hundred and eighty churches, mainly built during the period from the eleventh to the sixteenth centuries but with a few ranging in age up until the mid-nineteenth century, have been visited to identify the building stones used. The distribution pattern of use of four building stones – Tunbridge Wells Sandstone, Hythe Formation Sandstone, Mixon Stone and Quarr Stone – is presented and analysed. These building stones show distinctive patterns of distribution, which are related to geological, geographical, economic, architectural and historical factors. The building stones native to West Sussex are of considerable geological interest as few quarries or other exposures showing these strata are now present.

Abstract Lecce stone is a fine bio-calcarenite, widely used in the Salento region (southern Italy) as a constituent material of the large-scale built cultural heritage. This stone is affected by serious deterioration problems, such as alveolization and biological attack. The extensive conservation work carried out over the last few decades has promoted large-scale studies of various aspects related to the stone's characteristics, its resources, and associated decay and conservation problems. The paper reviews the main features of ‘Lecce stone’, addressing the following points: distribution of the quarries, including quarrying and carving techniques; mineralogical–petrographical and physical–mechanical characteristics of the extracted materials; use of the stone from antiquity until modern times; morphology of decay and, most importantly, decay factors; conservation treatments (products, tools and techniques), with particular reference to case studies of Baroque monuments; and systematic monitoring of monuments treated in the last 20 years. Given the wide spectrum of activities conducted in connection with Lecce monuments, and the stone from which they are built, they may be regarded as a suitable model for the study and management of monumental heritage in terms of its preservation.

Abstract Three Romanesque churches of the Bourbonnais region in the French Massif Central have been investigated. These date back to the twelfth century, and are mainly built of red and white sandstones. Their ashlar blocks were extensively repointed in the mid-twentieth century with cement-rich mortar. In order to quantitatively assess the impact of repointing on the decay rates of the sandstones, the following methods have been used: dating of reference surfaces (‘zero datum levels’) based on stone-dressing marks, stone-by-stone and terrestrial LiDAR (Light Detection And Ranging) surveys, and petrographical analyses including on-site non-destructive tests. This study reveals that, between the twelfth century and the mid-twentieth century, intrinsic geological factors have been a key control on weathering rates. Stone surface recession has proceeded, on average, 500 times faster in the poorly cemented soft white sandstone compared to the iron-cemented red sandstone (4 mm/century v. 0.008 mm/century). Since the mid-twentieth century, the replacement of the original lime mortar with a cement-rich mortar has resulted in a marked increase in weathering rates and resulting surface recession of the poorly cemented white sandstone: this increase is fivefold where cement-lime mortar (‘bastard mortar’) has been used and 10-fold where harder cement-rich mortar has been applied. By contrast, the application of cement-lime mortar between the ashlars composed of iron-cemented red sandstone had no deleterious effects. This study confirms that the use of cement-based mortar should be avoided on soft and porous masonries. It also stresses the fact that accelerated stone surface recession rates are systematically associated with heritage sites that are subject to significant anthropogenic effects caused by inappropriate interventions or excessive pressure on the monuments or their environment.

Abstract Long-term performance of historic buildings can be affected by many environmental factors, some of which become more apparent as the competence of the fabric deteriorates. Many tall historic buildings suffer from water ingress when exposed to driving rain conditions, particularly church towers in the SW of England. It is important to recognize that leakage can occur not only through flaws in the roof of a building but also through significant thicknesses of solid masonry. Identification of the most appropriate intervention requires an understanding of the way in which water might enter the structure and the assessment of potential repair options. While the full work schedule used an integrated assessment involving laboratory, field and archival work to assess the repairs that might be undertaken on these solid wall structures, this paper focuses on the laboratory work carried out to inform the writing of a Technical Advice Note on the effects of wind-driven rain and moisture movement in historic structures. The laboratory work showed that grouting and rendering were effective at reducing water penetration without retarding drying rates, and that use of internal plastering also had a very beneficial effect.

Abstract There is considerable academic and practical interest in stone and stone buildings, as exemplified by the wide range of high-quality and innovative work being conducted in the pursuit of the effective preservation and restoration of historic buildings. This is reflected in the numerous publications on stone and stone buildings that regularly find their way into the public domain. Not least amongst these are a number of Geological Society Special Publications, which have appeared in recent years. This current volume seeks to bring to the attention of the various professionals in the field (geologists, architects, engineers, conservators and conservation scientists) recent work centred on the characterization and performance of this important resource and its use in historic buildings. The volume has wider relevance, including to those interested in the heritage of stone.