Mineral phase
IMA name
Quartz polymorphs
Type
Class
silicate mineral
Compound type
tektosilicate
Comments
mostly Si Tetrahedral Frameworks SiO2 with [4] coordinated Si, except Stishovite
Phase diagram of silica polymorphs (from The Quartz Page)
Chemical composition
Formula
$SiO_2$
Chemical formula
SiO2
Elemental formula
Si O2
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Si$ Silicon element 1 constituent element main
$O$ Oxygen element 2 constituent element main
Chemical bonds
  Bond Number
$\geq Si-O-$ 4
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)

Dana

Major class
silicates (VIII)
Class
tectosilicate Si tetrahedral frameworks (75)
Type
SiO2 with [4] coordinated Si (75.01)
Group
N/A (N/A)
Polymorphs
Phase type
crystalline
Crystal system
various
Crystal class
various
Crystal class symbol
various
Crystal spacegroup
various
Composition order
ordered
Molar mass
60.08 $g/mol$
Density
2.25 - 4.35 $g/cm^3$
State NTP
solid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-solid alpha-Quartz <-> beta-Quartz 573°C at 1 bar, ~1190°C at ~3.1 GPa
solid-solid beta-Quartz <-> beta-Trydimite 597 K (870°C) at 100 kPa, 0.7 GPa at 1470°C
solid-solid alpha-Tridymite <-> beta-Trydimite 390 K (117°C)
solid-solid beta-Trydimite <-> beta-Cristobalite 1197 K (1470°C)
solid-solid beta-Quartz <-> beta-Cristobalite between 1197 K - 1432 K (1470°C - 1705°C) 0.8 - 1 GPa
solid-solid alpha-Cristobalite <-> beta-Cristobalite 543 K (270°C)
solid-solid alpha-Quartz <-> Coesite below 1.9 GPa at room T, below 3.1 GPa at 1180°C
solid-solid beta-Quartz <-> Coesite below 3.1 GPa at 1180°C, below 4.4 GPa at 2200°C
solid-solid Coesite <-> Stishovite Stishovite: metastable below 7.9 GPa at room T, below 11 GPa at 1400°C
solid-liquid beta-Quartz <-> liquid SiO2 1550°C (1 GPa) - ~2400°C (~4.5 GPa)
solid-liquid beta-Cristobalite <-> liquid SiO2 1705°C
Refringence type
various
Birefringence
0.003 - 0.027
Refraction index $n_{\alpha}$
1.468 - 1.800
Refraction index $n_{\beta}$
1.470 - 1.845
Refraction index $n_{\gamma}$
1.474 - 1.599
Dispersion V
none
Pure color
colorless
Color
colorless, blue-gay, brown, violet, gray, yellow
Diaphaneity
transparent to translucent
Luster
vitreous
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