Bertrandite
Mineral Be4Si2O7(OH)2
About it
Small, thin tabular crystals, often heart-shaped twins, in beryllium pegmatites; at Spor Mountain, Utah, it is the main beryllium ore.
- Type
- Mineral
- Group
- Silicate (sorosilicate), bertrandite group
- Formula
- Be4Si2O7(OH)2
- Hardness (Mohs)
- 6–7
- Specific gravity
- 2.59–2.6
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Orthorhombic
- Colours
- colourless, white, pale yellow
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in one direction
Typical values: real specimens vary. For more, see mindat.org.