Coesite

Dora Maira Massif, Cuneo Province, Piedmont, Italy
© Sergey Vasiliev

Show Coesite Photos (2)

Formula:

SiO

System:

Monoclinic

Colour:

Colourless

Lustre:

Vitreous

Hardness:

7½ - 8

Name:

For Loring Coes Jr. (1915-1978), American chemist who first synthesized it.

Polymorph of:

Cristobalite, Quartz, Stishovite, Tridymite

This page provides mineralogical data about Coesite.

Classification of Coesite

IMA status:

Approved

Strunz 8th edition ID:

4/D.01-50

Nickel-Strunz 10th (pending) edition ID:

4.DA.35

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
A : With small cations: Silica family

Dana 8th edition ID:

75.1.4.1

75 : TECTOSILICATES Si Tetrahedral Frameworks
1 : Si Tetrahedral Frameworks - SiO₂ with [4] coordinated Si

Hey's CIM Ref.:

7.8.2

7 : Oxides and Hydroxides
8 : Oxides of Si

mindat.org URL:

http://www.mindat.org/min-1104.html
Please feel free to link to this page.

Type Occurrence of Coesite

Type Locality:

Meteor Crater (Barringer Crater), Winslow, Coconino Co., Arizona, USA

Year of Discovery:

1954

Occurrences of Coesite

Geological Setting:

Formed at pressures > 20 kbar. Impact craters, kimberlites, eclogites.

Physical Properties of Coesite

Lustre:

Vitreous

Diaphaneity (Transparency):

Transparent

Colour:

Colourless

Hardness (Mohs):

7½ - 8

Cleavage:

Poor/Indistinct
Suspected on {010}{012}

Fracture:

Sub-Conchoidal

Density (calculated):

2.92 g/cm³

Crystallography of Coesite

Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Space Group:

B2/b {B1 1 2/b} {C2/c} {C1 2/c 1}

Cell Parameters:

a = 7.143(2) Å, b = 12.383(3) Å, c = 7.143(2) Å
β = 120°

Ratio:

a:b:c = 0.577 : 1 : 0.577

Unit Cell Volume:

V 547.16 Å³ (Calculated from Unit Cell)

Morphology:

Irregular to rectangular grains.

Optical Data of Coesite

Type:

Biaxial (+)

RI values:

n_α = 1.593 - 1.599 n_γ = 1.597 - 1.604

2V:

Measured: 54° to 64°

Maximum Birefringence:

δ = 0.004 - 0.005

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.

Surface Relief:

Moderate

Dispersion:

r < v weak

Comments:

On synthetic material

Chemical Properties of Coesite

Formula:

SiO

Essential elements:

O, Si

All elements listed in formula:

O, Si

Common Impurities:

Al,Fe,Na

Relationship of Coesite to other Species

4.DA.05

Quartz

SiO

4.DA.10

Opal

SiO

·nH

4.DA.10

Tridymite

SiO

4.DA.15

Cristobalite

SiO

4.DA.20

Mogánite

SiO

4.DA.25

Melanophlogite

46SiO

·6(N

,CO

)·2(CH

)

4.DA.30

Lechatelierite

SiO

4.DA.40

Stishovite

SiO

4.DA.45

Keatite

4.DA.50

Seifertite

SiO

7.8.1

Quartz

SiO

7.8.3

Tridymite

SiO

7.8.4

Stishovite

SiO

7.8.5

Cristobalite

SiO

7.8.6

Lechatelierite

SiO

7.8.7

Silhydrite

3SiO

·H

7.8.8

Opal

SiO

·nH

7.8.9

Mogánite

SiO

Other Names for Coesite

Other Languages:

German:	Coesit
Russian:	Коэсит
Spanish:	Coesita

Other Information

Health Warning:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Coesite

Reference List:

Chao, E.C.T., et al (1960), First natural occurrence of coesite, Science: 132: 220-222.

American Mineralogist (1960): 45: 1313.

American Mineralogist (1962): 47: 1292-1302.

Fahey, J.J. (1964), Recovery of coesite and stishovite from Coconino Sandstone of Meteor Crater, AZ, American Mineralogist: 49: 1643-1647.

Bohn, E. & W. Stöber (1966), Coesit und Stishovit als isolierte natürliche Mineralien, Neues Jahrb. Min.: 89-96.

Zeitschrift für Kristallographie: 145: 108-123.

Bohlen, S.R. and Boettcher, A.L. (1982) The quartz-coesite transformation: a precise determination and the effects of other components. Journal of Geophysical Research: 87(B8): 7073-7078.

Zhang, J., Li, B., Utsumi, W., and Liebermann, R.C. (1996) In situ X-ray observations of the coesite-stishovite transition: reversed phase boundary and kinetics. Physics and Chemistry of Minerals: 23: 1-10.

Gibbs, G.V., M.B. Boisen, Jr., .M. Rosso, D.M. Teter, & M..T. Bukowinski (2000), Model structures and electron density distribution for the silica polymorph coesite at pressure: An assessment of OO bonded interactions: Journal of Physical Chemistry: B: 104: 10534-10542.

Mosenfelder, J.L. (2000) Pressure dependence of hydroxyl solubility in coesite. Physics and Chemistry of Minerals 27(9): 610-617.