cubic Halides
Fluorite (Interpenetrating Twin)
Formula CaF2
Crystal Structure
#! Species: Fluorite
#! System: Cubic (m3m)
#! Habit: Interpenetrating cube twin at 60°
cubic[m3m]:{100}@1.0 | twin(fluorite)
cubic
m3m
{100}
Quick Facts
Hardness
4.0
Specific Gravity
3.18
Refractive Index
1.434
Optical Character
Isotropic
Physical Properties
- Crystal System
- cubic
- Hardness (Mohs)
- 4.0
- Specific Gravity
- 3.18
- Cleavage
- Perfect octahedral {111}
- Fracture
- Subconchoidal to uneven
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.434
- Optical Character
- Isotropic
- Dispersion
- 0.007
- Pleochroism
- None
- Fluorescence
- Often strong (blue, green, or violet) - source of the term 'fluorescence'
Characteristics
Colours
Purple (most common)GreenBlueYellowPinkColourlessMulticoloured (zoned)
Localities
ChinaMexicoEngland (Derbyshire, Durham)USA (Illinois)SpainMorocco
Common Inclusions
Colour zoningTwo-phase fluid inclusionsSolid inclusions
Known Treatments
Irradiation (rare)Coating (rare)
Crystal Forms
cube
Diagnostic Features
Perfect octahedral cleavage {111}; strong fluorescence; isotropic; low hardness (4)
Notes
Penetration twin with 60 degree rotation around [111] axis; highly prized by collectors
Related Minerals
Other minerals in the cubic system
