Achroite
Variety Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
About it
Colourless tourmaline, rare because nearly all tourmaline carries some colour. Mostly a collector's stone, found as small crystals in lithium pegmatites.
- Type
- Variety
- Group
- Elbaite variety (tourmaline)
- Formula
- Na(Li1.5Al1.5)Al6(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
- colourless
- Transparency
- transparent
- Cleavage and fracture
- poor; uneven to conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.