Bayldonite on dioptaseBright green crystals of this rare secondary mineral have grown above a beauti

Bayldonite on dioptaseBright green crystals of this rare secondary mineral have grown above a beautiful cluster of dioptase crystals (see http://tinyurl.com/n4lj2nc for a description) from the Tsumeb mine in Namibia. Named after the man who bought is off a mineral dealer for analysis it in the English county of Cornwall, its composition is lead copper arsenate, and it forms when fluids alter and oxidise primary sulphide ores in polymetallic deposits. Its usual colour is bright green from its copper content, but yellowy green and black are also possible. Crystals are rare, it usually forms as botryoidal crusts on top of other minerals. Bayldonite has sometimes been cut into cabochons for collectors, but its scarcity makes this uncommon. Alongside England, it has turned up in France, Ireland, Namibia, Kazakhstan, Australia, and the United States. The lush specimen in the photo measures 2.5 x 2.3 x 1.4 cm.LozImage credit: Joe Budd/Rob Lavinsky/iRocks.comhttp://www.mindat.org/min-581.htmlhttp://www.dakotamatrix.com/mineralpedia/5112/bayldonitehttp://www.galleries.com/Bayldonite -- source link

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