Quartz replacing Anhydrite

Item Description

These iconic and certainly distinctive "casts" from the San Juan Mountains of Colorado for years were labeled as Quartz after Baryte, but it's important to note that that Baryte is almost chemically inert and nearly impossible to dissolve, so it seemed unlikely that it could be replaced by Quartz solutions. In recent years, it has been confirmed that these pieces are in fact "casts" of Quartz replacing Anhydrite. The first report I saw came from Dr. Virgil Lueth at New Mexico Tech who concluded that these and all San Juan Quartz epimorphs/perimorphs are replacing Anhydrite, and it has been agreed upon by the mineral community. With that said, this specimen is a beautiful big, showy pseudomorph / cast consisting sugary white Quartz replacing dozens of thin "spade"-shaped tabular blades of Anhydrite measuring up to 3.5 cm. You can actually see some slight hollow indentations/impressions where the Anhydrite has been dissolved away, and the Quartz filled in, so there is a slight "cast" aspect to the piece, but whether you want to call them "casts" or pseudomorphs, this piece is a notably impressive and essentially damage-free large cabinet example of this classic material.
Ex George Loud Collection No. 210 CO.40; 10,221. George (born August 16, 1942) is a well-known mineral collector from Washington, DC and South Carolina respectively, and was a patent lawyer by trade for over 50 years. He assembled one of the great mineral collections in the U.S., comprising worldwide specimens, and in later years he sold the worldwide specimens to focus on minerals of the United States, specifically locality suites with an emphasis on amazing representation of species while still maintaining fine quality. The specimens remarkably range from micros to all the way up to large cabinets in size. We recently acquired most of his impressive 9000+ piece collection, and the VAST majority of these pieces will be offered here in the auctions, as we feel that everyone deserves and equal opportunity at acquiring these important, well-documented and fine quality specimens for their collections.
See: https://mineralogicalrecord.com/biographies_labels/george-loud for more information