Tridymite
Mineral SiO2
About it
Thin six-sided plates, often twinned in threes or wedge shapes, lining cavities in rhyolite and andesite. A high-temperature silica; good specimens from Cerro San Cristóbal, Mexico, and the Eifel, Germany.
- Type
- Mineral
- Group
- Silicate (tectosilicate), silica group
- Formula
- SiO2
- Hardness (Mohs)
- 7
- Specific gravity
- 2.25–2.28
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Triclinic
- Colours
- colourless, white
- Transparency
- transparent, translucent
- Cleavage and fracture
- poor prismatic; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.