CornetiteThe number of colourful minerals encountered in the zones of copper ore deposits that have
CornetiteThe number of colourful minerals encountered in the zones of copper ore deposits that have been altered by fluids of varied chemistry passing through during the course of geological time is considerable, and many of them form the core of collections. Here the primary sulphide minerals have been converted into oxidised minerals (see http://bit.ly/1I4XWKt for an explanation of this term) dependent on the chemistry of the fluids, with the well known carbonates malachite and azurite being the best known example. Cornetite is a rarity, a copper phosphate found in many places, but the best specimens (including the one in the photo) come from the Star of the Congo Mine in the Democratic republic of Congo. It was named after a Belgian geologist named Jules Cornet.Colour varies from blue to green, with all the mixtures between, usually in deep saturated hues (saturation indicates the depth of a colour, pink is a lightly saturated red for example, as opposed to tone which delineates how light or dark a colour is). It is too soft for jewellery or carving use, with a Mohs hardness of 4.5. The specimen featuring radial sprays of crystals in the photo is from the type locality mentioned above in D.R. Congo, and measures 3.8 x 2.5 x 2.4 cm.LozImage credit: Rob Lavinsky/iRocks.comhttp://www.mindat.org/min-1131.htmlhttp://bit.ly/1VNDxUlhttp://www.galleries.com/Cornetite -- source link
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