Chrome tourmaline
Variety NaMg3Al6(Si6O18)(BO3)3(OH)3(OH)
About it
Deep green tourmaline coloured by chromium and vanadium, mostly dravite rather than elbaite. Found in Tanzania and Kenya; often a purer green than ordinary iron-coloured green tourmaline.
- Type
- Variety
- Group
- Dravite variety (tourmaline)
- Formula
- NaMg3Al6(Si6O18)(BO3)3(OH)3(OH)
- Hardness (Mohs)
- 7–7.5
- Specific gravity
- 3–3.26
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Trigonal
- Colours
- intense green
- Transparency
- transparent
- Cleavage and fracture
- poor; uneven to conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.