phosphates
Torbernite
Cu(UO2)2(PO4)2·12H2O
- Also known as
- copper uranitechalcolite
- Crystal system
- tetragonal
- Hardness
- 2–2.5 on the Mohs scale
- Lustre
- vitreous
- Colour
- Emerald to grass green
- Where it forms
- By oxidation of uranium ores in the presence of copper and phosphate.
- Chiefly from
- Cornwall, EnglandKatanga, Democratic Republic of the CongoGermanyPortugal
Why it is that colour
Copper and the uranyl ion together. Unlike autunite it does not fluoresce, because the copper quenches it.
Safety
Radioactive, and with an additional specific hazard: torbernite dehydrates at ordinary room temperature into metatorbernite, and in doing so it crumbles. A specimen degrading in a warm dry room is producing radioactive dust. Keep it sealed and humid if kept at all, never handle bare-handed, and never bring it near food or a bedroom.
Where it comes from
Historic Cornish material from the copper and tin mines. Congolese material from Katanga is associated with the Shinkolobwe mine, whose uranium was used in the Manhattan Project.
Historical use
Cornish miners called it copper uranite. Its Congolese occurrence at Shinkolobwe produced the highest-grade uranium ore ever found, and the uranium in the Hiroshima bomb came largely from there.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
Worth knowing
Torbernite is the more dangerous of the two common uranium micas to keep, for a reason that has nothing to do with how radioactive it is. It holds twelve waters of crystallisation, it loses them at ordinary room temperature, and as it does the crystals break down. A collector who leaves it in a warm dry cabinet finds it has become powder — radioactive powder, in an open drawer.
The usual advice is to store it sealed with a small amount of moisture, or not to collect it at all.
Identity checked against IMA-CNMNC master list, June 2025.