Dioptase.Copper sulphides when deposited are a grey or golden colour, but get some groundwater passi
Dioptase.Copper sulphides when deposited are a grey or golden colour, but get some groundwater passing through a copper deposit to alter them into secondary minerals and some stunning hues result. Dioptase is mostly found in arid regions, and it’s mode of formation is more complex than say copper carbonates like malachite. Silica is poorly soluble in the acidic waters that usually permeate sulphide deposits (the same that cause acid mine/rock drainage pollution), but when carbonates are also present, minute amounts of copper silicates may be formed over a long time, including our suspect above and chrysocolla.With its low hardness of 5 on Moh’s scale, it is unsuitable for jewellery, though it has been faceted sometimes for collectors. This is quite tricky as it has three directions of perfect or good cleavage, and cutting must take place at an angle to all of these, or layers of the mineral will lift off when placed on the polishing wheel. With stunning mineral specimens like these, who would want to break them up anyway? Faceted gems or crystals will shatter along the cleavage planes if exposed to the rigours of ultrasonic cleaning.Like many brightly coloured minerals (such as azurite, cinnabar, realgar and orpiment) dioptase has been used since time immemorial in homemade pigments and paints. The best specimens come from the Tsumeb mine in Namibia (see http://bit.ly/1c2CjkD), a world famous site for many copper minerals, and a name likely to evoke an avid light in any mineral collector’s eyes. This 3.3 x 2.4 x 1.1 cm crystal group comes from a different mine, also in Namibia.LozImage credit: Rob Lavinsky/iRocks.comhttp://www.galleries.com/Dioptasehttp://www.mindat.org/min-1295.htmlhttp://www.webmineral.com/data/Dioptase.shtml__ -- source link
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