Mineral phase
- IMA name
- beta-Cristobalite
- Secondary names
- Cristobalite, high-cristobalite
- Class
- silicate mineral
- Compound type
- tektosilicate
- 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.15
Dana
- Major class
- silicates (VIII)
- Class
- tectosilicate Si tetrahedral frameworks (75)
- Type
- SiO2 with [4] coordinated Si (75.01)
- Group
- Cristobalite group (75.01.01)
- Code
- 75.01.01.01
- Phase name
- beta-Cristobalite
- Phase type
- crystalline
- Crystal system
- isometric (cubic)
- Crystal class
- hexoctahedral
- Crystal class symbol
- m-3m (Oh)
- Crystal spacegroup
- Fd-3m
- Comments
- The cubic β phase consists of dynamically disordered silica tetrahedra
- Molar mass
- 60.08 $g/mol$
- Density
- 2.27 $g/cm^3$
- State NTP
- solid
- Phase transitions
-
Phase transition type Other phases Temperature - Pressure solid-solid alpha-Cristobalite below 543 K (270°C) solid-solid beta-Quartz between 1197 K - 1432 K (1470°C - 1705°C) 0.8 - 1 GPa solid-solid beta-Trydimite below 1197 K (1470°C) solid-liquid liquid SiO2 above 1432 K (1705°C) - Phase transitions comments
- the stable phase at NTP is alpha-quartz
- Refringence type
- isotropic
- Refringence sign
- no
- Birefringence
- 0
- Refraction index $n_{\alpha}$
- 1.479
- Pure color
- colorless
- Color
- colorless, white
- Diaphaneity
- transparent to translucent
- Luster
- vitreous