Coffinite
Mineral U(SiO4)1-x(OH)4x
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
Black, dull uranium silicate that replaces plant matter in sandstone, a main ore of the Colorado Plateau and New Mexico's Grants district; rarely seen as visible crystals.
- Type
- Mineral
- Group
- Silicate (nesosilicate), zircon group
- Formula
- U(SiO4)1-x(OH)4x
- Hardness (Mohs)
- 5–6
- Specific gravity
- 5.1
- Lustre
- dull, adamantine (diamond-like)
- Crystal system
- Tetragonal
- Colours
- black
- Transparency
- opaque
- Cleavage and fracture
- none; irregular to subconchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.