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Enstatite

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Big Photo

Bronzite
Summit Rock, Klamath Co., Oregon, USA
© Saul Krotki 2003




Formula:
MgSiO
 
3
System:OrthorhombicColour:White, yellowish green, ...
Lustre:Vitreous, PearlyHardness:5 - 6
Member of:Orthopyroxene Subgroup > Pyroxene Group
Name:From the Greek enstates - "opponent" for refractory nature under blowpipe flame.
Polymorph of:Akimotoite, Clinoenstatite


Enstatite Group. Enstatite-Ferrosilite Series.

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Classification of Enstatite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/F.02-10
Nickel-Strunz 10th (pending) edition ID:9.DA.05

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
Dana 8th edition ID:65.1.2.1

65 : INOSILICATES Single-Width,Unbranched Chains,(W=1)
1 : Single-Width Unbranched Chains, W=1 with chains P=2
Hey's CIM Ref.:14.4.2

14 : Silicates not Containing Aluminum
4 : Silicates of Mg
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Occurrences of Enstatite

Geological Setting:Magmatic mafic rocks

Physical Properties of Enstatite

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

Crystallography of Enstatite

Crystal System:Orthorhombic
Class (H-M):mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:Pbca
Cell Parameters:a = 18.23Å, b = 8.84Å, c = 5.19Å
Ratio:a:b:c = 2.062 : 1 : 0.587
Unit Cell Volume: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.
Crystal Atlas:
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Enstatite no.12 - Goldschmidt (1913-1926)
Enstatite no.67 - Goldschmidt (1913-1926)

About Crystal Atlas

The mindat.org Crystal Atlas allows you to view a selection of crystal drawings of real and idealised crystal forms for this mineral and, in certain cases, 3d rotating crystal objects. The 3d models and HTML5 code are kindly provided by www.smorf.nl.

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Enstatite

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°
Maximum Birefringence:δ = 0.009 - 0.011

Chart 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 Enstatite

Formula:
MgSiO
 
3
Simplified for copy/paste:MgSiO3
Essential elements:Mg, O, Si
All elements listed in formula:Mg, O, Si
Common Impurities:Fe,Ca,Al,Co,Ni,Mn,Ti,Cr,Na,K

Relationship of Enstatite to other Species

Series:Forms a series with Ferrosilite (see here)
Member of:Orthopyroxene Subgroup > Pyroxene Group
Other Members of Group:

- +
Donpeacorite
(Mn
2+
 
,Mg)Mg[SiO
 
3
]
 
2
Ferrosilite
FeSiO
 
3
Related Minerals - Nickel-Strunz Grouping):

- +
9.DA.05Donpeacorite
(Mn
2+
 
,Mg)Mg[SiO
 
3
]
 
2
9.DA.05Ferrosilite
FeSiO
 
3
9.DA.10Clinoenstatite
MgSiO
 
3
9.DA.10Clinoferrosilite
Fe
2+
 
SiO
 
3
9.DA.10Kanoite
Mn
2+
 
(Mg,Mn
2+
 
)Si
 
2
O
 
6
9.DA.10Pigeonite
(Mg,Fe
2+
 
,Ca)(Mg,Fe
2+
 
)Si
 
2
O
 
6
9.DA.15Augite
(Ca,Na)(Mg,Fe
2+
 
,Al,Fe
3+
 
,Ti)[(Si,Al)
 
2
O
 
6
]
9.DA.15Diopside
CaMgSi
 
2
O
 
6
9.DA.15Esseneite
CaFe
3+
 
[AlSiO
 
6
]
9.DA.15Hedenbergite
CaFe
2+
 
Si
 
2
O
 
6
9.DA.15Johannsenite
CaMn
2+
 
Si
 
2
O
 
6
9.DA.15Petedunnite
Ca(Zn,Mn
2+
 
,Mg,Fe
2+
 
)Si
 
2
O
 
6
9.DA.15Davisite
CaScAlSiO
 
6
9.DA.15Kushiroite
CaAl[AlSiO
 
6
]
9.DA.15Grossmanite
CaTi
3+
 
AlSiO
 
6
9.DA.20Aegirine-augite
(Na,Ca)(Fe
3+
 
,Fe
2+
 
,Mg,Al)Si
 
2
O
 
6
9.DA.20Omphacite
(Ca,Na)(Mg,Al)Si
 
2
O
 
6
9.DA.25Aegirine
NaFe
3+
 
Si
 
2
O
 
6
9.DA.25Jadeite
Na(Al,Fe
3+
 
)Si
 
2
O
 
6
9.DA.25Jervisite
(Na,Ca,Fe
2+
 
)(Sc,Mg,Fe
2+
 
)Si
 
2
O
 
6
9.DA.25Kosmochlor
NaCrSi
 
2
O
 
6
9.DA.25Namansilite
NaMn
3+
 
Si
 
2
O
 
6
9.DA.25Natalyite
Na(V
3+
 
,Cr)Si
 
2
O
 
6
9.DA.30Spodumene
LiAlSi
 
2
O
 
6
Related Minerals - Hey's Index Grouping:

- +
14.4.1Forsterite
Mg
 
2
SiO
 
4
14.4.3Clinoenstatite
MgSiO
 
3
14.4.4Chrysotile
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
14.4.5Clinochrysotile
14.4.6Orthochrysotile
14.4.7Parachrysotile
14.4.8Lizardite
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
14.4.9Talc
Mg
 
3
(Si
 
4
O
 
10
)(OH)
 
2
14.4.10Spadaite
MgSiO
 
2
(OH)
 
2
· H
 
2
O (?)
14.4.11Sepiolite
Mg
 
4
(Si
 
6
O
 
15
)(OH)
 
2
· 6H
 
2
O
14.4.12Loughlinite
Na
 
2
Mg
 
3
Si
 
6
O
 
16
· 8H
 
2
O
14.4.13Eifelite
KNa
 
3
Mg
 
4
Si
 
12
O
 
30
14.4.14Stevensite
(Ca,Na)
 
x
Mg
 
3-x
(Si
 
4
O
 
10
)(OH)
 
2
14.4.15Antigorite
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
14.4.16 Magnesio-anthophyllite

Other Names for Enstatite

Synonyms:
AmblystegiteChladniteEnstaditeFiciniteO-enstatite
OrthobronziteOrthoenstatitePaulitePeckhamiteProtobastite
SheparditeShepardite (of Rose)Victorite
Other Languages:
German:Amblystegit
Chladnit
Cladnit
Enstadit
Enstatit
Ficinit
O-enstatit
Orthobronzit
Orthoenstatit
Paulit
Peckhamit
Protobastit
Shepardit
Victorit
Russian:Энстатит
Simplified Chinese:顽火辉石
顽辉石
Spanish:Amblystegita
Chladnita
Enstadita
Enstatita
Ficinita
Orthobronzita
Orthoenstatita
Paulita
Peckhamita
Protobastita
Shepardita
Victorita
Traditional Chinese:頑火輝石
頑輝石
Varieties:
BronziteLime-BronziteVanadinbronzite

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 Enstatite

Reference List:

- +
Klaproth, M.H. (1810): Chemische Untersuchung des Bronzits, Beiträge zur chemischen Kenntniss der Mineralkörper, Fünfter Band, Rottmann Berlin, 32-36

Morimoto, N. and Koto, K. (1969) The crystal structure of orthoenstatite. Zeitschrift für Kristallographie: 129: 65-83.

Anastasiou, P. and 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. and 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., and Ito, J. (1977) Synthesis and crystal structure refinement of transition-metal orthopyroxenes. I: orthoenstatite and (Mg,Mn,Co) orthopyroxene. Canadian Mineralogist: 15: 321-338.

Weidner, D.J., Wang, H., and Ito, J. (1978) Elasticity of orthoenstatite. Physics of the Earth and Planetary Interiors 17: 7-13.

Ralph, R.L. and 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.

Zeitschrift für Kristallographie (1986): 176: 159.

Duffy, T.S. and Vaughan, M.T. (1988) Elasticity of enstatite and its relationship to crystal structure. Journal of Geophysical Research: 93: 383-391.

Angel, R.J. and 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. and Angel, R.J. (1994) A compressional study of MgSiO3 orthoenstatite up to 8.5 GPa. American Mineralogist: 79: 405-410.

Yang, H. and 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., and Shankland, T.J. (1995) A high P-T single-crystal X-ray diffraction study of thermoelasticity of MgSiO3 orthoenstatite. Pysics and Chemistry of Minerals: 22: 393-398.

Flesch, L.M., Li., B., and 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., and 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., and Zha, C. (2001) High-temperature single-crystal elasticity and thermal exansion of orthoenstatite. Eos (Fall Meeting Supplement), Abstract T31C-0853.

Angel, R.J. and 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., and Tazzoli, V. (2002a) 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., and Tazzoli, V. (2002b) Mixing properties of the enstatite-ferrosilite solid solution: II A microscopic perspective. Eurpean 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., and 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., and 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., and 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 Enstatite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Enstatite details from Handbook of Mineralogy (PDF)
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    Localities for Enstatite

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