Torbernite, whose name derives from the Swedish chemist Tornbern Bergmann (1735-1784), is a radioactive, green phosphate mineral, found in granites and other uranium-bearing deposits as a secondary mineral. Torbernite is isostructural with a related uranium mineral, autunite, with torbernite's lack of fluorescence a notable difference.
Uses of torbernite
As a radioactive mineral, torbernite has some significance as an ore of uranium. Its rich color and distinctive crystals make it a sought after collectors mineral, as well. However, torbernite, like other hydrated minerals, suffers from loss of water molecules. This loss of water from the mineral leads to an alteration of all torbernite specimens into its pseudomorph, meta-torbernite. Some collector's sites assert than any torbernite specimen more than a few years old should be considered fully transitioned to meta-torbernite.
As torbernite is radioactive, collectors are urged to take proper precautions in the handling and storage of any specimens.
Torbernite frequently occurs in conjunction with other uranium minerals, as well as host rock minerals. These associated minerals include:
autunite, Ca(UO2)2(PO4)2 · 8-12H2O
uranophane, Ca}}(UO2)2Si2O7 · 6H2O
uranocircite, Ba(UO2)2(PO4)2 · 8-12H2O
Torbernite's most common alternative names are copper uranite and cuprouranite.
Notes for identification
The most obvious factor in identifying torbernite is its radioactivity. However, since it is frequently found in association with other radioactive minerals, this may not be useful in separating one uranium mineral from the rest. A next step would be to check color. Most uranium-bearing minerals are bright yellow or green. As torbernite is exclusively green, this can be a useful secondary fact. Crystal habit is also useful, but as it shares a similar structure and color with autunite, torbernite's lack of fluorescence can distinguish the two. Nonetheless, regardless of identification, it is likely that at least some of the specimen will have already altered to meta-torbernite.