Emeralds? No, these are not emeralds. Among the more than 3500 mineral species defined by the IMA – International Mineralogical Association, there are a few that would have became popular gemstones, only if they were a bit more durable for everyday jewellery wear. Dioptase is one of those cases.
This hydrous copper silicate with a characteristic emerald-green to blue-green colour has a relatively high dispersion (δ = 0.052) and would be a top choice as a cut gemstone if it wasn’t for its low hardness (5 in the Mohs scale), its brittleness, and perfect cleavage.
Dioptase was named by famed French mineralogist René Just Haüy in 1797 precisely because of one of these properties, from the Greek “through” and “to see,” alluding to the visibility of internal cleavage planes.
From the three main characteristics that are typically associated with a gemstone, “beauty” is there, “rarity” is also there, but not durability. It is, however, a rather popular mineral among collectors and connoisseurs, especially in its typical rhombohedral crystal clusters.
Jewellery artist Andrew Grima (1921-2007) that was known for using the unusual, made this gold and diamond pendant in 1973 with a fine dioptase cluster (on the right) © Bonhams. On the left, a fine two-crystal dioptase on a calcite specimen from the famous Tsumeb mine in Namibia, collection of Bill Severance © Jeff Scovil.
Guest articles by Rui Galopim de Carvalho:
https://gem-spectrum.com/category/rui-galopim-de-carvalho
About the author:
Rui Galopim de Carvalho is a renowned independent Gem Education Consultant, author, luxury industry training expert and popular international lecturer on gemmology and on the history of gem materials. During his 30 year experience as a gemmologist, Rui has studied important collections in both public and private museums, notably the Portuguese Crown Jewels.
Founder of the popular Home Gemmology webinar series launched during the COVID-19 lockdown, Rui has a long history as a gemmology communicator, notably on social media where he is a popular figure.
Rui Galopim de Carvalho can be reached through his website:
