Quartz

Quartz
General
CategorySilicate mineral[1]
Formula
(repeating unit)
SiO2
IMA symbolQz[2]
Strunz classification4.DA.05 (oxides)
Dana classification75.01.03.01 (tectosilicates)
Crystal systemα-quartz: trigonal
β-quartz: hexagonal
Crystal classα-quartz: trapezohedral (class 3 2)
β-quartz: trapezohedral (class 6 2 2)[3]
Space groupα-quartz: P3221 (no. 154)[4]
β-quartz: P6222 (no. 180) or P6422 (no. 181)[5]
Unit cella = 4.9133 Å, c = 5.4053 Å; Z = 3
Identification
Formula mass60.083 g·mol−1
ColorColorless, pink, orange, white, green, yellow, blue, purple, dark brown, or black
Crystal habit6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive
TwinningCommon Dauphine law, Brazil law, and Japan law
Cleavage{0110} Indistinct
FractureConchoidal
TenacityBrittle
Mohs scale hardness7 – lower in impure varieties (defining mineral)
LusterVitreous – waxy to dull when massive
StreakWhite
DiaphaneityTransparent to nearly opaque
Specific gravity2.65; variable 2.59–2.63 in impure varieties
Optical propertiesUniaxial (+)
Refractive indexnω = 1.543–1.545
nε = 1.552–1.554
Birefringence+0.009 (B-G interval)
PleochroismNone
Melting point1670 °C (β tridymite); 1713 °C (β cristobalite)[3]
SolubilityInsoluble at STP; 1 ppmmass at 400 °C and 500  lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2[3]
Other characteristicsLattice: hexagonal, piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic)
References[6][7][8][9]

Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is, therefore, classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.[10]

Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C (846 K; 1,063 °F). Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold.

There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Europe and Asia.

Quartz is the mineral defining the value of 7 on the Mohs scale of hardness, a qualitative scratch method for determining the hardness of a material to abrasion.

  1. ^ "Quartz". A Dictionary of Geology and Earth Sciences. Oxford University Press. 19 September 2013. ISBN 978-0-19-965306-5.
  2. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  3. ^ a b c Deer, W. A.; Howie, R.A.; Zussman, J. (1966). An introduction to the rock-forming minerals. New York: Wiley. pp. 340–355. ISBN 0-582-44210-9.
  4. ^ Antao, S. M.; Hassan, I.; Wang, J.; Lee, P. L.; Toby, B. H. (1 December 2008). "State-Of-The-Art High-Resolution Powder X-Ray Diffraction (HRPXRD) Illustrated with Rietveld Structure Refinement of Quartz, Sodalite, Tremolite, and Meionite". The Canadian Mineralogist. 46 (6): 1501–1509. doi:10.3749/canmin.46.5.1501.
  5. ^ Kihara, K. (1990). "An X-ray study of the temperature dependence of the quartz structure". European Journal of Mineralogy. 2 (1): 63–77. Bibcode:1990EJMin...2...63K. doi:10.1127/ejm/2/1/0063. hdl:2027.42/146327.
  6. ^ Quartz Archived 14 December 2005 at the Wayback Machine. Mindat.org. Retrieved 2013-03-07.
  7. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (29 January 1990). "Quartz" (PDF). Handbook of Mineralogy. Vol. III (Halides, Hydroxides, Oxides). Chantilly, VA: Mineralogical Society of America. ISBN 0962209724. Archived (PDF) from the original on 1 April 2010. Retrieved 21 October 2009.
  8. ^ Quartz Archived 12 November 2006 at the Wayback Machine. Webmineral.com. Retrieved 2013-03-07.
  9. ^ Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20 ed.). Wiley. ISBN 0-471-80580-7.
  10. ^ Anderson, Robert S.; Anderson, Suzanne P. (2010). Geomorphology: The Mechanics and Chemistry of Landscapes. Cambridge University Press. p. 187. ISBN 978-1-139-78870-0.