Cristobalite(alpha)

Formula : SiO2

Family: 
Space group: 
Tetragonal - Trapezohedral H-M Symbol (4 2 2) Space Group: P 41212
Dana class: 
75.1.1.1 (75) Tectosilicate Si Tetrahedral Frameworks (75.1)SiO2 with [4] coordinated Si (75.1.1) Dana Group
High temperature: 
Above approximately 1470C to the melting point of silica round 1713C.Alpha cristobalite undergoes a first phase transition at 200C-275C, from cubic to tetragonal phase beta cristobalite.
Geological context: 
Present in volcanic rocks, it form from molten rock at temperatures above approximately 1470 degrees Celsius to the melting point of silica (around 1713C)

Dernière mise à jour le 11.06.2018

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
cm3·mol-1
ΔGºf
J·mol-1
ΔHºf
J·mol-1
J·mol-1·k-1
CP
J·mol-1·K-1
60.084 25.740 -852989 -906030 46.060 44.32
Reaction properties

Cristobalite(alpha) + 2H2O ⇌ H4SiO4

298.15 K, 1 bar log10K: -3.16 ΔH°r: 16496 J·mol-1
T(°C) 0 25 60 100 150 200 250 300
log10K -3.43 -3.16 -2.86 -2.57 -2.28 -2.06 -1.87 -1.73