Coesite | SSHADE

Mineral phase

IMA name: Coesite

Class: silicate mineral
Compound type: tektosilicate

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 functions and bonds

Chemical bonds

	Bond	Number
	$\geq Si-O-$	4

Oxides composition

Oxides

Formula	$SiO_{2}$
Mass fraction (%)	100.0

Classifications

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.35

Dana

Major class: silicates (VIII)
Class: tectosilicate Si tetrahedral frameworks (75)
Type: SiO2 with [4] coordinated Si (75.01)
Group: -Coesite- group (75.01.04)
Code: 75.01.04.01

Crystallography

Phase type: crystalline
Crystal system: monoclinic
Crystal class: prismatic
Crystal class symbol: 2/m (C2h)
Crystal spacegroup: C2/c

Physical properties

Molar mass: 60.08 $g/mol$
Density: 2.93 $g/cm^3$

Thermodynamical properties

State NTP

solid

Phase transitions

Phase transition type	Other phases	Temperature - Pressure
solid-solid	Stishovite (metastable below 7.9 GPa at room T, below 11 GPa at 1400°C)	metastable below 1.9 GPa at room T, below 4.2 GPa at 2200°C
solid-solid	alpha-Quartz	below 1.9 GPa at room T, below 3.1 GPa at 1180°C
solid-solid	beta-Quartz	below 3.1 GPa at 1180°C, below 4.4 GPa at 2200°C

Phase transitions comments

the stable phase at NTP is

α - Q u a r t z

$\alpha-Quartz$

Optical properties

Refringence type: biaxial
Refringence sign: positive
Birefringence: 0.0050-0.0060
Refraction index $n_{\alpha}$: 1.593-1.594
Refraction index $n_{\beta}$: 1.595
Refraction index $n_{\gamma}$: 1.599
Pure color: colorless
Color: colorless
Diaphaneity: transparent
Luster: vitreous

Links and Publications

Links