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Forsterite

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Formula:
Mg2SiO4
Colour:
Green, pale yellow or white.
Lustre:
Vitreous
Hardness:
7
Specific Gravity:
3.275
Crystal System:
Orthorhombic
Member of:
Name:
Known in ancient times and some smaragdus and beryllos (Pliny, 79) may have been what is now called forsterite. (N.B. The "chrysolithas" of Pliny (79) is believed to be topaz.) The earliest name given to an undisputed olivine group species was chrysolit (chrysolite) and was named by Johan Gottschalk Wallerius in 1747, although the name chrysolite was later used by Balthasar Georges Sage in 1777 for what is now known as prehnite. In 1755, Antoine Joseph Dezallier d'Argenville called this species "peridot ordinaire", while Axel Cronstedt named it "gulgron topas" in 1758. In 1772, Rome d'Lisle renamed the mineral "chrysolite ordinaire". Wallerius's chrysolite was renamed, olivine, in 1789 by Abraham Gottlieb Werner for the usual olive green color of this mineral (N.B. chrysolite has a similar etymology.) Friedrich Walchner in 1823 gave it the name "hyalosiderite". Named forsterite in 1824 by Serve-Dieu Abailard "Armand" Lévy in honor of Adolarius Jacob Forster [April 6, 1739, Grossbreitenbach, Thuringia, Germany - May 1806 St. Petersburg, Russia], German mineral collector and mineral dealer, who variously resided in England and Russia. Boltonite was introduced in 1835 by Charles Upham Shepard, while glinkit was named in 1847 by Romanovski.
Polymorph of:
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Classification of ForsteriteHide

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

9 : SILICATES (Germanates)
A : Nesosilicates
C : Nesosilicates without additional anions; cations in octahedral [6] coordination
51.3.1.2

51 : NESOSILICATES Insular SiO4 Groups Only
3 : Insular SiO4 Groups Only with all cations in octahedral [6] coordination
14.4.1

14 : Silicates not Containing Aluminum
4 : Silicates of Mg

Physical Properties of ForsteriteHide

Vitreous
Transparency:
Transparent, Translucent
Colour:
Green, pale yellow or white.
Streak:
White
Hardness:
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {010}
imperfect on {100}
Fracture:
Conchoidal
Density:
3.275 g/cm3 (Measured)    3.271 g/cm3 (Calculated)

Optical Data of ForsteriteHide

Type:
Biaxial (+)
RI values:
nα = 1.636 - 1.730 nβ = 1.650 - 1.739 nγ = 1.669 - 1.772
2V:
Measured: 74° to 90°, Calculated: 56° to 84°
Max Birefringence:
δ = 0.033 - 0.042
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r > v or r < v

Chemical Properties of ForsteriteHide

Formula:
Mg2SiO4
Common Impurities:
Fe

Crystallography of ForsteriteHide

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 4.754 Å, b = 10.1971 Å, c = 5.9806 Å
Ratio:
a:b:c = 0.466 : 1 : 0.587
Unit Cell V:
289.92 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Euhedral to subhedral crystals
Twinning:
{100} {011} {012}
Comment:
Data for synthetic material.

X-Ray Powder DiffractionHide

Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
d-spacingIntensity
5.15 (20)
3.916 (40)
3.744 (10)
3.516 (30)
3.481 (10)
3.030 (10)
3.014 (10)
2.791 (100)
2.601 (10)
2.578 (5)
2.533 (60)
2.475 (60)
2.391 (5)
2.370 (20)
2.330 (5)
2.285 (30)
2.270 (30)
2.173 (10)
2.048 (5)
1.962 (5)
1.894 (10)
1.823 (5)
1.807 (10)
1.761 (50)
1.754 (10)
1.743 (10)
1.684 (10)
1.654 (10)
1.644 (5)
1.631 (20)
1.604 (10)
1.586 (10)
1.523 (5)
1.513 (5)
1.508 (20)
1.494 (20)
1.407 (10)
1.397 (10)
1.359 (10)
Comments:
ICDD 31-795 for composition Fo64 ; See also ICDD 33-657 (ferroan forsterite); and ICDD 34-189 (synthetic)

Type Occurrence of ForsteriteHide

Synonyms of ForsteriteHide

Other Language Names for ForsteriteHide

Simplified Chinese:镁橄榄石
Traditional Chinese:鎂橄欖石

Varieties of ForsteriteHide

PeridotA green gem variety of Forsterite

Relationship of Forsterite to other SpeciesHide

Member of:
Other Members of this group:
Calcio-olivineCa2SiO4Orth. mmm (2/m 2/m 2/m)
FayaliteFe2+2SiO4Orth.
GlaucochroiteCaMn2+SiO4Orth.
KirschsteiniteCaFe2+SiO4Orth. mmm (2/m 2/m 2/m) : Pnma
LaihuniteFe2+Fe3+2(SiO4)2Mon.
Liebenbergite(Ni,Mg)2SiO4Orth.
MonticelliteCaMgSiO4Orth.
OlivineEquivalent to Fayalite-Forsterite Series; usually a more or less Fe-bearing forsterite.Orth.
Roepperite (of Brush)(Fe2+2,Mn,Zn)SiO4
TephroiteMn2+2SiO4Orth. mmm (2/m 2/m 2/m)
Forms a series with:

Common AssociatesHide

Associated Minerals Based on Photo Data:
Spinel96 photos of Forsterite associated with Spinel on mindat.org.
Calcite71 photos of Forsterite associated with Calcite on mindat.org.
Magnetite14 photos of Forsterite associated with Magnetite on mindat.org.
Phlogopite10 photos of Forsterite associated with Phlogopite on mindat.org.
Ludwigite8 photos of Forsterite associated with Ludwigite on mindat.org.
Diopside7 photos of Forsterite associated with Diopside on mindat.org.
Chromian Diopside6 photos of Forsterite associated with Chromian Diopside on mindat.org.
Kamacite6 photos of Forsterite associated with Kamacite on mindat.org.
Quartz6 photos of Forsterite associated with Quartz on mindat.org.
Taenite5 photos of Forsterite associated with Taenite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.AC.AhrensiteFe2SiO4Iso. m3m (4/m 3 2/m)
9.AC.05FayaliteFe2+2SiO4Orth.
9.AC.05GlaucochroiteCaMn2+SiO4Orth.
9.AC.05KirschsteiniteCaFe2+SiO4Orth. mmm (2/m 2/m 2/m) : Pnma
9.AC.05LaihuniteFe2+Fe3+2(SiO4)2Mon.
9.AC.05Liebenbergite(Ni,Mg)2SiO4Orth.
9.AC.05TephroiteMn2+2SiO4Orth. mmm (2/m 2/m 2/m)
9.AC.10MonticelliteCaMgSiO4Orth.
9.AC.15BrunogeieriteFe2+2Ge4+O4Iso. m3m (4/m 3 2/m) : Fd3m
9.AC.15Ringwoodite(Mg,Fe2+)2SiO4Iso. m3m (4/m 3 2/m) : Ia3d
9.AC.20ChesnokoviteNa2[SiO2(OH)2] · 8H2OOrth. mmm (2/m 2/m 2/m) : Ibca

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

51.3.1.1FayaliteFe2+2SiO4Orth.
51.3.1.3Liebenbergite(Ni,Mg)2SiO4Orth.
51.3.1.4TephroiteMn2+2SiO4Orth. mmm (2/m 2/m 2/m)
51.3.1.5LaihuniteFe2+Fe3+2(SiO4)2Mon.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

14.4.2EnstatiteMgSiO3Orth. mmm (2/m 2/m 2/m) : Pbca
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.

Forsterite in petrologyHide

An essential component of (items highlighted in red)
Common component of (items highlighted in red)

References for ForsteriteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Dana, E.S. (1892) System of Mineralogy, 6th. Edition, New York: 450-451, 451-456 (as chrysolite).
Kushiro, I. (1969) The system forsterite-diopside-silica with and without water at high pressures: American Journal of Science: 267: 269-294.
Hazen, R.M. (1976) Effects of temperature and pressure on the crystal structure of forsterite. American Mineralogist: 61: 1280-1293.
Deer, W.A., Howie, R.A., Zussman, J. (1982) Rock-Forming Minerals. Volume 1A. Orthosilicates. Longmans, 2nd. Edition, 919 pp.: 3-336.
Francis, C.A. (1985) New data on the forsterite-tephroite series. American Mineralogist: 70: 568-575.
Zha, C.-S., Duffy, T.S., Downs, R.T., Mao, H.-K., Hemley, R.J. (1996) Sound velocities and elasticity of single-crystal forsterite to 16 GPa. Journal of Geophysical Research: 101(B8): 17535-17545.
Brodholt, J.P. (1997) Ab initio calculations on point defects in forsterite (Mg2SiO4) and implications for diffusion and creep: American Mineralogist: 82: 1049-1053.
Brodholt, J.P., Refson, K. (2000) An ab initio study of hydrogen in forsterite and a possible mechanism for hydrolytic weakening. Journal of Geophysical Research: 105: 18977-18982.
Xue, X., Kanzaki, M., Turner, D., Loroch, D. (2017): Hydrogen incorporation mechanisms in forsterite: New insights from 1H and 29Si NMR spectroscopy and first-principles calculation. American Mineralogist: 102: 519–536.

Internet Links for ForsteriteHide

Localities for ForsteriteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListShow

Mineral and/or Locality  
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