Chrysocolla, Tyrolite, Clinotyrolite

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This thumbnail specimen was part of a much larger specimen presented to the Philadelphia Academy by Dr. Domeyko in the late 1800s, who did much work on the rare minerals of Chile and Argentina. Regardless of the chemistry, the specimen has merit as a display piece of beautiful copper combinations from Chile. This piece has beautiful, powder-blue chrysocolla forming as stalactitic growths and as a thin carpet in the few hollow vugs inside a matrix of nearly solid tyrolite. On analysis by modern equipment, the matrix material shows to be tyrolite, clinotyrolite, and possibly other related species admixed (XRAY and powder, Bart Cannon's lab, 2008). However, apparently the official mineralogy of tyrolite classification is confusing and has changed over time. Clinotyrolite is often considered a species by many people, though without IMA approval. I quote MINDAT's page on the matter verbatim to make sure I do not mistakenly convey the science: Since it is well-known that also carbonate-free varieties of tyrolite exist, "tyrolite" may actually represent two or more minerals/polytypes. At least two monoclinic polytypes of tyrolite are known (Krivovichev et al., 2006); one of them seems to be identical to "clinotyrolite." Note that this is the first report of the locality to MINDAT for tyrolite occurence, but it is likely that this rare species is present on other old specimens of "chrysocolla" from Chile. Ex. Academy of Natural Sciences Philadelphia Collection.