tetragonal Oxides
Cassiterite
Formula SnO2
Crystal Structure
#! Species: Cassiterite
#! System: Tetragonal (4/mmm)
#! Habit: Short prismatic with dominant dipyramid
tetragonal[4/mmm]:{100}@0.8[striation:parallel] + {101}@1.0 + {111}@0.4
tetragonal
4/mmm
{100} {101} {111}
Quick Facts
Hardness
6.5
Specific Gravity
6.85
Refractive Index
1.997
Optical Character
Uniaxial +
Physical Properties
- Crystal System
- tetragonal
- Hardness (Mohs)
- 6.5
- Specific Gravity
- 6.85
- Cleavage
- Poor prismatic {100}
- Fracture
- Subconchoidal to uneven
- Lustre
- Adamantine to vitreous
Optical Properties
- Refractive Index
- 1.997
- Birefringence
- 0.096-0.098
- Optical Character
- Uniaxial +
- Dispersion
- 0.071
- Pleochroism
- moderate: Yellow-green / Reddish-brown (Variable; strong in colored material, absent in colorless; dichroic)
Characteristics
Colours
BrownBlackReddish-brownYellowColourless (rare - gem quality)
Localities
BoliviaChina (Yunling, Yunnan)IndonesiaMalaysiaCornwall (England - historic)Myanmar
Common Inclusions
FracturesTwinningFluid inclusions
Crystal Forms
tetragonal_prismtetragonal_dipyramid
Notes
Called Andean diamond in Bolivia; dispersion (0.071) is twice that of diamond; faceted gems are rare collectors items
Related Minerals
Other minerals in the tetragonal system
