Constituent
- Name
- Tridymite
- IMA name
- alpha-Tridymite
- Class
- silicate mineral
- Compound type
- tektosilicate
- Relevance
- main - major
- Arrangement
- single phase
- Abundance comments
- Probable traces
- Formula
- $SiO_2$
- Chemical formula
- SiO2
- Elemental formula
- Si O2
- Isotope mixture type
- terrestrial abundance
- Oxides
-
Formula $SiO_{2}$ Mass fraction (%) 100.0
Strunz
- Class
- oxides - hydroxides - arsenites (04)
- Division
- metal:oxygen = 1:2 and similar (04.D)
- Family
- with small cations: Silica family (04.DA)
- Code
- 04.DA.10
Dana
- Major class
- silicates (VIII)
- Class
- tectosilicate Si tetrahedral frameworks (75)
- Type
- SiO2 with [4] coordinated Si (75.01)
- Group
- -Tridymite- group (75.01.02)
- Code
- 75.01.02.01
- Phase name
- alpha-Tridymite
- Phase type
- crystalline
- Crystal system
- orthorhombic
- Crystal class
- disphenoidal
- Crystal class symbol
- 222 (D2)
- Crystal spacegroup
- C222(1)
- Comments
- Classified by mineralogists as triclinic-pedial, 1 (C1) / F1
- Molar mass
- 60.08 $g/mol$
- Density
- 2.28 - 2.33 $g/cm^3$
- Refringence type
- biaxial
- Refringence sign
- positive
- Birefringence
- 0.003 - 0.006
- Refraction index $n_{\alpha}$
- 1.468 - 1.482
- Refraction index $n_{\beta}$
- 1.470 - 1.484
- Refraction index $n_{\gamma}$
- 1.474 - 1.486
- Dispersion V
- none
- Color
- colorless, white, yellowish white, gray
- Diaphaneity
- transparent to translucent
- Luster
- vitreous