Mineral christmas treeAn amazing natural composition of twinned crystals of colourful radioactive mi

Mineral christmas treeAn amazing natural composition of twinned crystals of colourful radioactive mineral has congealed from the fires of the Earth into a shape reminiscent of a currently popular symbol.Named after a Swedish chemist, torbernite is born in granites which concentrate the world’s radioactive (amongst other) elements that don’t fit into the common mantle minerals. The granites then spit out fluids containing these elements (which don’t really fit in the common granitic minerals either) as they cool.These fluid remnants are enriched in all sorts of things, and the source of many of our metals and gemstones. One of the most common types of such deposits are called copper (+-gold) porphyries, and it is in uranium rich examples of these that torbernite forms. It is an uncommon secondary mineral, produced when the primary uranium containing minerals in the ore deposit are altered and eroded in the usual ways (ie wind and rain, percolating water, plants and bacteria etc).It consists of hydrated copper uranyl phosphate, and is closely related to another mineral called autunite (which we covered before at http://on.fb.me/1JKDqjU). It displays perfect cleavage along the basal plane of the crystal, like a book of mica (it has been called uranmica). These lines of weakness are areas with minimal atomic bonds holding the crystal structure together.Popular with collectors, it is a delicate mineral, prone to losing its water. The mineral needs special storage (gas tight and humidified) both for its preservation and due to its radioactivity, and should be stored away from other minerals since it might affect their colour. It outgases radon, so special care in opening storage containers, ventilating the storage space and handling specimens should be taken.Localities include the ancient mining area of Cornwall in England, Germany, the USA and the Ayeron department France, where this 3x3x2cm specimen hails from.LozImage credit: Rob Lavinsky/iRocks.com -- source link

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