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Enstatite

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Formula:
MgSiO3
Colour:
White, yellowish green, brown, greenish white or grey, olive-green
Lustre:
Vitreous, Pearly
Hardness:
5 - 6
Specific Gravity:
3.2 - 3.9
Crystal System:
Orthorhombic
Name:
From the Greek enstates - "opponent" for refractory nature under blowpipe flame.
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Classification of EnstatiteHide

Approved, 'Grandfathered' (first described prior to 1959)
9.DA.05

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
65.1.2.1

65 : INOSILICATES Single-Width,Unbranched Chains,(W=1)
1 : Single-Width Unbranched Chains, W=1 with chains P=2
14.4.2

14 : Silicates not Containing Aluminum
4 : Silicates of Mg

Physical Properties of EnstatiteHide

Vitreous, Pearly
Transparency:
Translucent, Opaque
Comment:
Pearly on cleavage
Colour:
White, yellowish green, brown, greenish white or grey, olive-green
Streak:
Grey to white
Hardness:
5 - 6 on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
Good on {210}
Parting:
on {100} and {010}
Fracture:
Irregular/Uneven
Density:
3.2 - 3.9 g/cm3 (Measured)    3.189 g/cm3 (Calculated)

Optical Data of EnstatiteHide

Type:
Biaxial (+)
RI values:
nα = 1.650 - 1.668 nβ = 1.652 - 1.673 nγ = 1.659 - 1.679
2V:
Measured: 54° to 90°, Calculated: 58° to 86°
Max Birefringence:
δ = 0.009 - 0.011
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r < v weak

Chemical Properties of EnstatiteHide

Formula:
MgSiO3
Common Impurities:
Fe,Ca,Al,Co,Ni,Mn,Ti,Cr,Na,K

Crystallography of EnstatiteHide

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Pbca
Cell Parameters:
a = 18.23 Å, b = 8.84 Å, c = 5.19 Å
Ratio:
a:b:c = 2.062 : 1 : 0.587
Unit Cell V:
836.39 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Prismatic crystals
Twinning:
The often reported "Simple and lamellar twinning on {100}" is no twinning (the symmetry plane is part of the crystal structure). Twinning may be confused with exsolution lamellae.

Crystallographic forms of EnstatiteHide

Crystal Atlas:
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Enstatite no.12 - Goldschmidt (1913-1926)
Enstatite no.67 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Transparency
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X-Ray Powder DiffractionHide

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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Synonyms of EnstatiteHide

Other Language Names for EnstatiteHide

Varieties of EnstatiteHide

BronziteA ferroan variety of enstatite
Lime-BronziteA Calcian Bronzite
VanadinbronziteA vanadium-bearing variety of enstatite.
Originally reported from Bracco, Genova Province, Liguria, Italy.

Relationship of Enstatite to other SpeciesHide

Other Members of this group:
Donpeacorite(Mn2+,Mg)Mg[SiO3]2Orth.
FerrosiliteFeSiO3Orth. mmm (2/m 2/m 2/m) : Pbca
Forms a series with:

Common AssociatesHide

Associated Minerals Based on Photo Data:
Pseudobrookite31 photos of Enstatite associated with Pseudobrookite on mindat.org.
Ilmenite21 photos of Enstatite associated with Ilmenite on mindat.org.
Tridymite21 photos of Enstatite associated with Tridymite on mindat.org.
Hematite19 photos of Enstatite associated with Hematite on mindat.org.
Zircon9 photos of Enstatite associated with Zircon on mindat.org.
Armalcolite-Pseudobrookite Series8 photos of Enstatite associated with Armalcolite-Pseudobrookite Series on mindat.org.
Diopside8 photos of Enstatite associated with Diopside on mindat.org.
Fluoro-edenite4 photos of Enstatite associated with Fluoro-edenite on mindat.org.
Sanidine4 photos of Enstatite associated with Sanidine on mindat.org.
Fluorapatite4 photos of Enstatite associated with Fluorapatite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.DA.05Donpeacorite(Mn2+,Mg)Mg[SiO3]2Orth.
9.DA.05FerrosiliteFeSiO3Orth. mmm (2/m 2/m 2/m) : Pbca
9.DA.10ClinoenstatiteMgSiO3Mon.
9.DA.10ClinoferrosiliteFe2+SiO3Mon.
9.DA.10KanoiteMn2+(Mg,Mn2+)Si2O6Mon. 2/m : P21/b
9.DA.10Pigeonite(CaxMgyFez)(Mgy1Fez1)Si2O6Mon. 2/m : P21/b
9.DA.15Augite(CaxMgyFez)(Mgy1Fez1)Si2O6Mon. 2/m : B2/b
9.DA.15DiopsideCaMgSi2O6Mon. 2/m : B2/b
9.DA.15EsseneiteCaFe3+[AlSiO6]Mon. 2/m : B2/b
9.DA.15HedenbergiteCaFe2+Si2O6Mon. 2/m : B2/b
9.DA.15JohannseniteCaMn2+Si2O6Mon. 2/m : B2/b
9.DA.15PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6Mon.
9.DA.15DavisiteCaScAlSiO6Mon. 2/m : B2/b
9.DA.15KushiroiteCaAl[AlSiO6]Mon. 2/m : B2/b
9.DA.15GrossmaniteCaTi3+ AlSiO6Mon. 2/m : B2/b
9.DA.20Aegirine-augite(NaaCabFe2+cMgd)(Fe3+eAlfFe2+gMgh)Si2O6Mon. 2/m : B2/b
9.DA.20Omphacite(NaaCabFe2+cMgd)(AleFe3+fFe2+gMgh)Si2O6Mon. 2/m
9.DA.25AegirineNaFe3+Si2O6Mon. 2/m : B2/b
9.DA.25JadeiteNa(Al,Fe3+)Si2O6Mon.
9.DA.25JervisiteNaSc3+Si2O6Mon.
9.DA.25KosmochlorNaCrSi2O6Mon.
9.DA.25NamansiliteNaMn3+Si2O6Mon.
9.DA.25NatalyiteNaV3+Si2O6Mon.
9.DA.30SpodumeneLiAlSi2O6Mon.

Related Minerals - Dana Grouping (8th Ed.)Hide

65.1.2.2FerrosiliteFeSiO3Orth. mmm (2/m 2/m 2/m) : Pbca
65.1.2.3Donpeacorite(Mn2+,Mg)Mg[SiO3]2Orth.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

14.4.1ForsteriteMg2SiO4Orth. mmm (2/m 2/m 2/m)
14.4.3ClinoenstatiteMgSiO3Mon.
14.4.4ChrysotileMg3(Si2O5)(OH)4Mon.
14.4.5ClinochrysotileMon. 2/m
14.4.6OrthochrysotileOrth.
14.4.7ParachrysotileOrth.
14.4.8LizarditeMg3(Si2O5)(OH)4
14.4.9TalcMg3Si4O10(OH)2Tric. 1 : P1
14.4.10SpadaiteMgSiO2(OH)2 · H2O (?)
14.4.11SepioliteMg4(Si6O15)(OH)2 · 6H2OOrth. mmm (2/m 2/m 2/m) : Pnna
14.4.12LoughliniteNa2Mg3Si6O16 · 8H2OOrth.
14.4.13EifeliteKNa3Mg4Si12O30Hex.
14.4.14Stevensite(Ca,Na)xMg3-x(Si4O10)(OH)2Mon.
14.4.15AntigoriteMg3(Si2O5)(OH)4Mon. m : Bm
14.4.16 Magnesio-anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2

Other InformationHide

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

Enstatite in petrologyHide

References for EnstatiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Klaproth, M.H. (1810) Chemische Untersuchung des Bronzits, Beiträge zur chemischen Kenntniss der Mineralkörper, Fünfter Band, Rottmann Berlin, 32-36.
Morimoto, N., Koto, K. (1969) The crystal structure of orthoenstatite. Zeitschrift für Kristallographie: 129: 65-83.
Anastasiou, P., Seifert, F. (1972) Solid solubility of Al2O3 in enstatite at high temperatures and 1-5 kb water pressure. Contributions to Mineralogy and Petrology: 34: 272-287.
Arima, M., Onuma, K. (1977) The solubility of alumina in enstatite and the phase equilibria in the join MgSiO3-MgAl2SiO6 at 10-25 kbar. Contributions to Mineralogy and Petrology: 61: 251-265.
Hawthorne, F.C., Ito, J. (1977) Synthesis and crystal structure refinement of transition-metal orthopyroxenes. I: orthoenstatite and (Mg,Mn,Co) orthopyroxene. The Canadian Mineralogist: 15: 321-338.
Weidner, D.J., Wang, H., Ito, J. (1978) Elasticity of orthoenstatite. Physics of the Earth and Planetary Interiors 17: 7-13.
Ralph, R.L., Ghose, S. (1980) Enstatite, Mg2Si2O6: compressibility and crystal structure at 21 kbar (abs.). Eos: 61: 409.
Ohashi, Y. (1984) Polysynthetically-twinned structures of enstatite and wollastonite. Physics and Chemistry of Minerals: 10: 217-229.
Ghose, S., Schomaker, V., Mcmullan, R.K. (1986) Enstatite, Mg2Si2O6 - a neutron-diffraction refinement of the crystal structure and a rigid-body analysis of the thermal variation. Zeitschrift für Kristallographie: 176: 159.
Duffy, T.S., Vaughan, M.T. (1988) Elasticity of enstatite and its relationship to crystal structure. Journal of Geophysical Research: 93: 383-391.
Angel, R.J., Hugh-Jones, D.A. (1994) Equation of state and thermodynamic properties of enstatite pyroxenes. Journal of Geophysical Research: 99: 19777-19783.
Hugh-Jones, D.A., Angel, R.J. (1994) A compressional study of MgSiO3 orthoenstatite up to 8.5 GPa. American Mineralogist: 79: 405-410.
Yang, H., Ghose, S. (1994) High-temperature single-crystal X-ray diffraction studies of the ortho-proto phase transition in enstatite, Mg2Si2O6 at 1360 K. Physics and Chemistry of Minerals: 22: 300-310.
Zhao, Y., Schiferl, D., Shankland, T.J. (1995) A high P-T single-crystal X-ray diffraction study of thermoelasticity of MgSiO3 orthoenstatite. Physics and Chemistry of Minerals: 22: 393-398.
Flesch, L.M., Li., B., Liebermann, R.C. (1998) Sound velocities of polycrystalline MgSiO3-orthopyroxene to 10 GPa at room temperature. American Mineralogist: 83: 444-450.
Jackson, J.M., Sinogeikin, S.V., Bass, J.D. (1999) Elasticity of MgSiO3 orthoenstatite. American Mineralogist: 84: 677-680.
Jackson, J.M., Palko, J., Sinogeikin, S.V., Bass, J.D., Andrault, D., Zha, C. (2001) High-temperature single-crystal elasticity and thermal expansion of orthoenstatite. Eos (Fall Meeting Supplement), Abstract T31C-0853.
Angel, R.J., Jackson, M.J. (2002) Elasticity and equation of state of orthoenstatite, MgSiO3. American Mineralogist: 87: 558-561.
Tarantino, S.C., Domeneghetti, M.C., Carpenter, M.A., Shaw, C.J.S., Tazzoli, V. (2002) Mixing properties of the enstatite-ferrosilite solid solution: I. A macroscopic perspective. European Journal of Mineralogy: 14: 525-536.
Tarantino, S.C., Boffa Ballaran, T., Carpenter, M.A., Domeneghetti, M.C., Tazzoli, V. (2002) Mixing properties of the enstatite-ferrosilite solid solution: II A microscopic perspective. European Journal of Mineralogy: 14: 537-547.
Lin, C.C. (2003) Pressure-induced metastable phase transition in orthoenstatite (MgSiO3) at room temperature: a Raman spectroscopic study. Journal of Solid State Chemistry: 174: 403-411.
Jackson, J.M., Sinogeikin, S.V., Carpenter, M.A., Bass, J.D. (2004) Novel phase transition in orthoenstatite. American Mineralogist: 89: 239-245.
Kung, J., Li, B.S., Uchida, T., Wang, Y.B., Neuville, D., Liebermann, R.C. (2004) In situ measurements of sound velocities and densities across the orthopyroxene - high-pressure clinopyroxene transition in MgSiO3 at high-pressure. Physics of the Earth and Planetary Interiors: 147: 27-44.
Nestola, F., Gatta, G.D., Ballaran, T.B. (2006) The effect of Ca substitution on the elastic and structural behavior of orthoenstatite. American Mineralogist: 91: 809-815.

Internet Links for EnstatiteHide

Localities for EnstatiteHide

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Mineral and/or Locality  
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