Mineralogical Data of Quartz


last modified: Tuesday, 26-May-2009 03:45:50 CEST

Table of Mineral Data

Mineralogical Classification
According to Dana
  - Si Tetrahedral Frameworks
According to Strunz 4/D.01-10: Oxides
Oxides with metal
to oxygen ratio of 1:2
  - Quartz Group
According to
Hey's Chemical Index of Minerals

Crystallographic Data
Crystal System Hexagonal / Trigonal
Crystal Class
Hermann Mauguin Symbols
Trigonal Trapezohedral
3 2
Space Group P3121 (left hand),
P3221 (right hand)
Unit Cell Data a = 4.9133, c = 5.4053
Ratio a:c = 1:1.10013

Optical Properties
Color colorless if pure,
otherwise any color
Streak none / white if pure
Luster vitreous
Cryptocrystalline: waxy to dull, vitreous if polished
Diapheny transparent if pure, otherwise transparent to opaque
Fluorescence none
Refractive Indices
for Na D-Line (589nm)
Cryptocrystalline: n = 1.53-1.54
Birefringence uniaxial positive:
ne-no = +0.00910
lower in cryptocrystalline quartz
Pleochroism / Dichroism none if pure, weak dichroism is observed in smoky quartz, amethyst, and certain citrines
Optical Activity
[γ]= degrees / mm
γ = 21.73°
for Na D-Line (589nm)

Electrical Properties
Relative Permittivity Dielectric Number
εr: 4.69 parallel to a-axis
εr: 5.06 parallel to c-axis
Behavior in Magnetic Fields diamagnetic

Mechanical Properties
Fracture conchoidal, sometimes uneven
Cleavage weak tendency to break along rhombohedral and prism planes
Tenacity brittle
Modulus of Elasticity
Mohs Hardness Macrocrystalline: 7
Cryptocrystalline: 6.5-7
Vicker's Indentation Hardness Macrocrystalline: average 1182 kg/mm2
(basal plane 1103 kg/mm2, prism faces 1260 kg/mm2)
Rosival Grinding Hardness Macrocrystalline: 100
(quartz is the reference)
Specific Weight 2.6481 g/cm3
Melting Point 1705°C
Boiling Point 2477°C
Thermal Expansion Coefficient
Thermal Conductivity
[λ] = W/m×K
λ = 12.14 parallel to c-axis
λ = 6.70 parallel to a-axis


Further Information, Literature, Links

A table of quartz properties can be found at mindat.org:

Another table at www.webmineral.com:

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