Johannite
Mineral Cu(UO2)2(SO4)2(OH)2·8H2O
Take care.
- Radioactive: Keep it in a closed, labelled box away from where people sit or sleep, handle it briefly, wash your hands after, and never grind or cut it.
About it
Bright green crusts and tiny prisms of a copper uranyl sulfate that form as uraninite weathers in damp mines. A classic from Jáchymov in the Czech Republic; radioactive.
- Type
- Mineral
- Group
- Sulfate, uranyl sulfate
- Formula
- Cu(UO2)2(SO4)2(OH)2·8H2O
- Hardness (Mohs)
- 2–2.5
- Specific gravity
- 3.2–3.4
- Streak
- pale green
- Lustre
- vitreous (glassy)
- Crystal system
- Triclinic
- Colours
- emerald green, grass green, yellowish green
- Transparency
- transparent, translucent
- Cleavage and fracture
- imperfect
Typical values: real specimens vary. For more, see mindat.org.