Boracite
Mineral Mg3B7O13Cl
About it
Hard, glassy cubes and pseudo-cubic crystals in salt and gypsum deposits, much harder than the salts around them. Known from Lüneburg and Stassfurt, Germany, and the Boulby potash mine in England.
- Type
- Mineral
- Group
- Borate, boracite group
- Formula
- Mg3B7O13Cl
- Hardness (Mohs)
- 7–7.5
- Specific gravity
- 2.91–3.1
- Streak
- white
- Lustre
- vitreous (glassy), adamantine (diamond-like)
- Crystal system
- Orthorhombic
- Colours
- colourless, white, grey, pale green, pale blue, yellow
- Transparency
- transparent, translucent
- Cleavage and fracture
- none; conchoidal to uneven fracture
Typical values: real specimens vary. For more, see mindat.org.