Coesite

Coesite
Crossed-polars image of coesite grain (gray) ~1 mm across in eclogite. Small, colored inclusion is pyroxene. Polycrystalline rim is quartz.
General
CategoryTectosilicate, quartz group
Formula
(repeating unit)
SiO2
IMA symbolCoe[1]
Strunz classification4.DA.35
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H–M symbol)
Space groupC2/c
Unit cella = 7.143
b = 12.383
c = 7.143 [Å]
β = 120.00°
Z = 16
Identification
Formula mass60.0843 g/mol
ColorColorless
Crystal habitInclusions in UHP metamorphic minerals up to 3 mm in size
FractureConchoidal
TenacityBrittle
Mohs scale hardness7.5-8
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density2.92 (calculated)
Optical propertiesBiaxial
Refractive indexnx = 1.594
ny = 1.595
nz = 1.599
Birefringence+0.006
2V angle60–70
References[2]

Coesite (/ˈkst/)[3] is a form (polymorph) of silicon dioxide (SiO2) that is formed when very high pressure (2–3 gigapascals), and moderately high temperature (700 °C, 1,300 °F), are applied to quartz. Coesite was first synthesized by Loring Coes, Jr., a chemist at the Norton Company, in 1953.[4][5]

  1. ^ 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.
  2. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1995). "Coesite" (PDF). Handbook of Mineralogy. Vol. 2 (Silica, Silicates). Chantilly, Virginia: Mineralogical Society of America. ISBN 0962209716. Retrieved December 5, 2011.
  3. ^ "coesite". Dictionary.com Unabridged (Online). n.d.
  4. ^ Coes, Jr., L. (31 July 1953). "A New Dense Crystalline Silica". Science. 118 (3057): 131–132. Bibcode:1953Sci...118..131C. doi:10.1126/science.118.3057.131. PMID 17835139. The word coesite is pronounced as "Coze-ite", after chemist Loring Coes, Jr.
  5. ^ Hazen, Robert M. (22 July 1999). The Diamond Makers. Cambridge University Press. p. 91. ISBN 978-0-521-65474-6. Retrieved 2012-06-06.