cubic Nesosilicates
Demantoid
Formula Ca3Fe2(SiO4)3:Cr
Crystal Structure
#! Species: Demantoid (Andradite Garnet)
#! System: Cubic (m3m)
#! Habit: Trapezohedron with diagnostic horsetail inclusions
cubic[m3m]:{211}@1.0[inclusion:horsetail] + {110}@0.7
cubic
m3m
{211} {110}
Quick Facts
Hardness
6.5
Specific Gravity
3.82
Refractive Index
1.888
Optical Character
Isotropic
Physical Properties
- Crystal System
- cubic
- Hardness (Mohs)
- 6.5
- Specific Gravity
- 3.82
- Cleavage
- None
- Fracture
- Conchoidal to uneven
- Lustre
- Adamantine to vitreous
Optical Properties
- Refractive Index
- 1.888
- Optical Character
- Isotropic
- Dispersion
- 0.057
- Pleochroism
- None (isotropic)
Characteristics
Colours
Vivid greenYellowish-greenGrass greenDeep green
Localities
Russia (Ural Mountains)NamibiaMadagascarIranItaly
Common Inclusions
Horsetail (byssolite/chrysotile fibres)Diopside crystalsMagnetite octahedra
Known Treatments
Heat treatment (rare, can improve colour)Generally not treated
Crystal Forms
trapezohedrondodecahedron
Related Minerals
Other minerals in the cubic system
