Coesite Mineral Data

General Coesite Information

Chemical Formula:

SiO2

Composition:

Molecular Weight = 60.08 gm

Silicon 46.74 % Si 100.00 % SiO₂

Oxygen 53.26 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

(SiO₂)

Environment:

High temperature and high pressure polymorph of quartz (500-800 deg C, ~ 30-35 kbar). Formed in impact craters and ultra-high-pressure eclogite rocks.

IMA Status:

Valid Species (Pre-IMA) 1954

Locality:

Metor Crater, Cononino County, Arizona, USA. Link to MinDat.org Location Data.

Name Origin:

Named for Loring Coes, Jr. (1915-1973), American chemist, Norton Company, who first synthesized the phase.

Synonym:

ICSD 18112

PDF 14-654

Coesite Image

Images:

Coesite

Comments: Fine-grained, massive coesite.
Location: Meteor Crater, Canyon Diablo, Coconino County, Arizona, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Coesite

Comments: Coesite inclusion in garnet of eclogite sample (Eur. J. Mineral, 13:567).
Location: Ultra high-pressure metamorphic area of the Saidenbach reservoir, Erzgebirge, Germany, where micro-diamond-bearing gneiss occurs. Scale: Scale Bar 50 µm.
© Eur. J. Mineral

Coesite Crystallography

Axial Ratios:

a:b:c =0.5791:1:0.5791

Cell Dimensions:

a = 7.17, b = 12.38, c = 7.17, Z = 16; beta = 120° V = 551.18 Den(Calc)= 2.90

Crystal System:

Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.098(1), 3.432(0.5), 2.77(0.15),

Physical Properties of Coesite

Cleavage:

None

Color:

Colorless.

Density:

2.93

Diaphaneity:

Transparent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Inclusions - Generally found as inclusions in other minerals.

Hardness:

7.5 - Garnet

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Coesite

Gladstone-Dale:

CI meas= 0.022 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.012 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2055,KPDmeas= 0.2034,KC= 0.208
Ncalc = 1.6 - 1.61

Optical Data:

Biaxial (+), a=1.593-1.594, b=1.595, g=1.599, bire=0.0050-0.0060, 2V(Calc)=54-72, 2V(Meas)=54-64. Dispersion r < v weak.

Calculated Properties of Coesite

Electron Density:

Bulk Density (Electron Density)=2.90 gm/cc
note: Specific Gravity of Coesite =2.90 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_Coesite= 1.80 barns/electron
U=PE_Coesite x rElectron Density= 5.20 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Coesite is Not Radioactive

Coesite Classification

Dana Class:

75.01.04.01 (75)Tectosilicate Si Tetrahedral Frameworks

(75.01)SiO2 with [4] coordinated Si

(75.01.04)Dana Group

75.01.04.01 Coesite SiO2 C 2/c 2/m

75.01.04.02 Moganite! SiO2 I2/a 2/m

Strunz Class:

04.DA.35 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.D - Metal:Oxygen = 1:2 and similar

04.DA -With small cations

04.DA.35 Coesite SiO2 C 2/c 2/m

Other Coesite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Dana8)

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Coesite

SiO2
Dana No: 75.01.04.01 Strunz No: 04.DA.35
Locality:

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