Formula: Cu(UO2)2(PO4)2.12H2O hydrated normal phosphate
Specific gravity: 3.3 to 3.7
Hardness: 2 to 2½
Colour: Emerald green
Solubility: Moderately soluble in hydrochloric, sulphuric and nitric acid
Uranium is a highly soluble, radioactive, heavy metal. It can be dissolved easily and transported by ground waters.
Also, it does not usually form very insoluble mineral species, which is a further factor in the wide variety of
environments and localities in which uranium minerals accumulate.
Within magmas uranium is an incompatible element (ie its size and charge do not allow it to combine easily with other components of the melt), and so the last part of granite melts to crystallise tends to become highly enriched in uranium, thorium and potassium and their compounds.
Uraninite is the most important ore of uranium, and torbernite and autunite are less important. (Wiki)
Torbernite is a secondary mineral found in the oxidation zones of some uranium-rich copper deposits, and as a coating of fissures in granite. It forms as an alteration product of uraninite or other uranium-bearing minerals, and it is associated with uraninite, autunite, carnotite and other phosphate minerals.
The copper Cu in the structure can be replaced by calcium Ca, forming autunite.
Above 60oC torbernite dehydrates to metatorbernite.
At the Block 14 Open Cut, Broken Hill, New South Wales, Australia, a few small crystals of torbernite have been found on pyromorphite crusts. (AJM 3.1.53)
At the South Alligator Valley Uranium Field, Northern Territories, Australia, the rare mineral threadgoldite is found coating or intergrown with torbernite/metatorbernite. (AJM 11.1.9)
At the Mount Isa Block, Queensland, Australia, just one small crystal of torbernite has been reported, associated with malachite. (AJM 17.2.86)
At the Mount Painter uranium deposit, Flinders Ranges, South Australia, torbernite of supergene origin occurs associated with ironstone (iron-rich sedimentary rock) and sometimes minor fluorite, baryte and quartz. (https://d28rz98at9flks.cloudfront.net/9761/Rec1945_067.pdf)
At the Hagendorf pegmatite, Bavaria, Germany, the dissolution of rockbridgeite releases (PO4)2- which leads to the precipitation of bassetite and then torbernite. In the presence of minor manganese, lehnerite may form, and in the presence of calcium, autunite may form. ( https://pubs.geoscienceworld.org/minmag/article-abstract/71/4/371/140367/ cu-fe-u-phosphate-mineralization-of-the-hagendorf?redirectedFrom=fulltext)
At the Apex Mine, Lander County, Nevada, USA, torbernite and metatorbernite occur in about equal proportions. Epitactic overgrowths of autunite on torbernite/metatorbernite have been found, and rare microcrystalline drusy crusts of jarosite. Baryte also occurs rarely in association with autunite and torbernite. (R&M 87.3.270-276)
Common impurities: Ca,Ba,Mg
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