Thorianite
Mineral ThO2
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
Heavy, black, cube-shaped crystals, often in penetration twins, washed from gem gravels and found in pegmatites. Strongly radioactive from thorium and uranium; Sri Lanka and Madagascar are classic sources.
- Type
- Mineral
- Group
- Oxide, uraninite group
- Formula
- ThO2
- Hardness (Mohs)
- 6–7
- Specific gravity
- 9.7–10
- Streak
- grey to greenish grey
- Lustre
- submetallic, resinous
- Crystal system
- Isometric (cubic)
- Colours
- dark grey, brownish black, black, greenish
- Transparency
- opaque
- Cleavage and fracture
- poor cubic; uneven to conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.