Andradite
Mineral Ca3Fe2(SiO4)3
About it
Calcium-iron garnet with strong lustre and fire: green demantoid from Russia and Namibia, black melanite in volcanic rock, and iridescent rainbow garnet from Japan and Mexico.
- Type
- Mineral
- Group
- Silicate (nesosilicate), garnet group
- Formula
- Ca3Fe2(SiO4)3
- Hardness (Mohs)
- 6.5–7
- Specific gravity
- 3.8–3.9
- Streak
- white
- Lustre
- adamantine (diamond-like), vitreous (glassy), resinous
- Crystal system
- Isometric (cubic)
- Colours
- black, brown, yellow, green, red-brown, iridescent
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- none; conchoidal to uneven fracture
Typical values: real specimens vary. For more, see mindat.org.