On an opening page of The San Juan Triangle of Colorado, the reader confronts a sweeping view of Red Mountain #2. This impressive image hints at the excellent articles and images to follow. This monograph is the first in the fifteen-volume series to highlight prolific U.S. mineral districts. The opening article, entitled, “Ho for the San Juans!” (D. Smith, M. Vendl, K. Vendl), provides an important historical perspective. Owing to logistical challenges, mining only really began in the region in the late 1800s. Key to this development was the railroad industry, which provided for economical transport of ores and spurred people to settle in various towns along the route. This article sets the stage nicely for those that follow: one senses not only the richness of the San Juan ores, but also appreciates the struggle associated with settling such rugged terrain.
In “Geology of the San Juan Mountains” (T. Wallace and T. Rosemeyer), the critical link between volcanism in the region and development of ore deposits is emphasized. For example, the Silverton collapsed caldera (~20 km diameter) provided the structural fabric for concentrating mineral deposits in the San Juan Triangle. The map of “Principle (sic) Mines and Specimen-Producing Localities in the San Juan Triangle” by W. Besse on p. 15 is invaluable for reference and regional context.
“The Camp Bird Mine” (T. Rosemeyer) treats the reader to a brief history of the mine, the geology and mineralogy of the different deposits, specimen mineralogy and collecting history. As an underground miner for 40 years, the knowledge and enthusiasm of Rosemeyer are evident throughout the text. A stunning photograph by J. Scovil of sphalerite and quartz (p. 30) highlights the quality of specimens from this mine. The specimen, now in the collection of D. Bunk, was originally in the collection of G. McWilliams.
The article “Crystal Collecting at the Idarado Mine” (J. Trujillo, A. Young and D. Earnest) is also written by miners who worked the mine. Their claim that the Idarado was one of the most prolific (quartz, calcite, gold, sphalerite, chalcopyrite, galena, fluorite, pyrite, barite and rhodochrosite) specimen-producing mines in the western U.S. is underscored by magnificent photographs.
“Quartz: The Crystal King of the Triangle” (T. Wallace and D. Bunk) documents the primary districts for spectacular crystallized quartz specimens. In “Rhodochrosite from the San Juans”, B. Muntyan discusses the key localities for this most sought-after of San Juan minerals. I particularly enjoyed her comparison of rhodochrosite from the San Juan triangle with the similarly famous rhodochrosite from the Pasto Bueno mine in Ancash, Peru. The article nicely complements the following “On the Sunnyside” (J. Murphy), as the Sunnyside is well known for aesthetic specimens of rhodochrosite, a stunning two-page photograph layout of which appears on pages 74–75.
There is an excellent balance between scientifically rich articles and engaging personal stories in the monograph. The articles on the “The Blue Sky People” (K. Stoufer), “The Indefatigable Benjy Kuehling” (G. Staebler), the adventures of Gary McWilliams in “The Right Place at the Right Time” (G. McWilliams) and “Ed McDole: Mineral Entrepreneur of the San Juans” (R. Eveleth) all provide welcome personal perspectives on the colorful and adventurous spirit that imbues the San Juan triangle.
Miscellaneous issues: typographical and grammatical errors occur sporadically throughout the text, e.g., inconsistencies on spelling within the same article [e.g., “silicious” on p. 18 and “siliceous” on p. 19, “Laramide orograny” (p. 43) and “of one of the its two main adits” (p. 46)]. An entire line was dropped on the bottom of p. 64. Then, on p. 54, the authors state that the Idarado calcite “crystals are typically translucent… with an opaque white band running through the center of the chain.” Unfortunately, this particular feature is nowhere clearly illustrated.
Minor issues aside, this monograph is an excellent read for anyone interested in the prolific mining history of the San Juan region. The spectacular images, attractive layouts and articles from authors directly linked to the region all combine to create an educational and engaging volume.