Colemanite
Mineral CaB3O4(OH)3·H2O
About it
Glassy, colourless, short prisms and geode-like nodules, harder than other common borates. Known from Death Valley, California, and Turkey's huge borate mines; named for borax businessman William T. Coleman.
- Type
- Mineral
- Group
- Borate
- Formula
- CaB3O4(OH)3·H2O
- Hardness (Mohs)
- 4.5
- Specific gravity
- 2.42
- Streak
- white
- Lustre
- vitreous (glassy), adamantine (diamond-like)
- Crystal system
- Monoclinic
- Colours
- colourless, white, grey, yellowish
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in one direction; uneven to subconchoidal fracture
- Under UV light
- often creamy white or yellowish under shortwave UV
Typical values: real specimens vary. For more, see mindat.org.