Hornblende
Mineral (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH)2
Also called Magnesio-hornblende and Ferro-hornblende
About it
Black to dark green six-sided prisms, the common amphibole of granite, diorite, and amphibolite; a name for several closely related species. Told from augite by its 56-degree cleavage.
- Type
- Mineral
- Group
- Silicate (inosilicate), amphibole group
- Formula
- (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH)2
- Hardness (Mohs)
- 5–6
- Specific gravity
- 3–3.5
- Streak
- white to greyish green
- Lustre
- vitreous (glassy)
- Crystal system
- Monoclinic
- Colours
- black, dark green, brown
- 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.