Shiny dioptase crystals from Tsumeb on matrix

Dioptase is a mineral belonging to the subclass of cyclosilicates. It was discovered by the German Rudolph Farber, towards the end of the eighteenth century, who misidentified it as a variety of emerald. Typically found in arid environments, Dioptase forms as a secondary mineral within the oxidized zones of copper sulfide deposits. Its genesis requires a delicate balance: while the oxidation of sulfides acidifies solutions, hindering the solubility of silica, dry climates and carbonate buffering allow trace silica to react with dissolved copper. This reaction favors the formation of Dioptase together with chrysocolla. The presence of brown quartzite distinguishes the samples, while those from Tsumeb, Namibia, are valued for their transparency. In other localities, such as the Mammoth-Saint Anthony mine, it forms as small crystals. In some occurrences, it is believed that Dioptase crystallizes together with quartz and copper.

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