Riebeckite
Mineral Na2(Fe3Fe2)Si8O22(OH)2
Also called Crocidolite and Blue asbestos
Take care.
- Can shed asbestos fibres: Keep it in a closed box, and never break, saw, sand, or scrape it.
About it
Dark blue to black prisms in alkali granite; its fibrous form, crocidolite, is the most hazardous asbestos. Tiger's eye from South Africa formed where quartz replaced crocidolite.
- Type
- Mineral
- Group
- Silicate (inosilicate), amphibole group
- Formula
- Na2(Fe3Fe2)Si8O22(OH)2
- Hardness (Mohs)
- 4–6
- Specific gravity
- 3.28–3.44
- Streak
- bluish grey
- Lustre
- vitreous (glassy), silky
- Crystal system
- Monoclinic
- Colours
- dark blue, black, blue-grey
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- perfect in two directions at about 56° and 124°
Typical values: real specimens vary. For more, see mindat.org.