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Fayalite

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Formula:
Fe22+SiO4
System:
Orthorhombic
Colour:
Greenish-yellow, yellow ...
Lustre:
Vitreous, Greasy
Hardness:
7
Member of:
Name:
Named by Christian Gottlibb Gmelin in 1840 for the type locality, Faial Island (Fayal Island), Azores District (Azores Islands), Portugal.
Polymorph of:
Olivine Group. Fayalite-Forsterite Series, and the Fayalite-Tephroite Series. The Fe2+ analogue of Forsterite, Tephroite, and Calcio-Olivine.

Uncommon in nature, but common in man-made (metallurgy) iron slags.
See also laihunite.

Visit gemdat.org for gemological information about Fayalite.

Classification of Fayalite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.AC.05

9 : SILICATES (Germanates)
A : Nesosilicates
C : Nesosilicates without additional anions; cations in octahedral [6] coordination
51.3.1.1

51 : NESOSILICATES Insular SiO4 Groups Only
3 : Insular SiO4 Groups Only with all cations in octahedral [6] coordination
14.19.1

14 : Silicates not Containing Aluminum
19 : Silicates of Fe
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First Recorded Occurrence of Fayalite

Year of Discovery:
1840

Physical Properties of Fayalite

Vitreous, Greasy
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Greenish-yellow, yellow or brown
Streak:
Colourless
Hardness (Mohs):
7

Crystallography of Fayalite

Crystal System:
Orthorhombic
Cell Parameters:
a = 4.79Å, b = 10.39Å, c = 6.06Å
Ratio:
a:b:c = 0.461 : 1 : 0.583
Unit Cell Volume:
V 301.59 ų (Calculated from Unit Cell)

Optical Data of Fayalite

Type:
Biaxial (-)
RI values:
nα = 1.731 - 1.824 nβ = 1.760 - 1.864 nγ = 1.773 - 1.875
2V:
Measured: 74° to 47°, Calculated: 54° to 66°
Max Birefringence:
δ = 0.042 - 0.051
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Very High
Dispersion:
weak

Chemical Properties of Fayalite

Formula:
Fe22+SiO4
Essential elements:
All elements listed in formula:
Common Impurities:
Mn

Relationship of Fayalite to other Species

Series:
Forms a series with Forsterite (see here)
Forms a series with Forsterite (see here)
Forms a series with Tephroite (see here)
Member of:
Other Members of Group:
Calcio-olivineCa2SiO4
ForsteriteMg2SiO4
GlaucochroiteCaMn2+SiO4
KirschsteiniteCaFe2+SiO4
LaihuniteFe2+Fe23+(SiO4)2
Liebenbergite(Ni,Mg)2SiO4
MonticelliteCaMgSiO4
Olivine(Mg,Fe2+)2SiO4
Roepperite (of Brush)(Fe22+,Mn,Zn)SiO4
TephroiteMn22+SiO4
9.AC.05ForsteriteMg2SiO4
9.AC.05GlaucochroiteCaMn2+SiO4
9.AC.05KirschsteiniteCaFe2+SiO4
9.AC.05LaihuniteFe2+Fe23+(SiO4)2
9.AC.05Liebenbergite(Ni,Mg)2SiO4
9.AC.05TephroiteMn22+SiO4
9.AC.10MonticelliteCaMgSiO4
9.AC.15BrunogeieriteFe22+Ge4+O4
9.AC.15Ringwoodite(Mg,Fe2+)2SiO4
9.AC.20ChesnokoviteNa2[SiO2(OH)2] · 8H2O
14.19.2FerrosiliteFeSiO3
14.19.3LaihuniteFe2+Fe23+(SiO4)2
14.19.4Ferro-anthophyllite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
14.19.5FerripyrophylliteFe23+(Si4O10)(OH)2
14.19.6GreenaliteFe2-3(Si2O5)(OH)4
14.19.7CronstedtiteFe22+Fe3+((Si,Fe3+)2O5)(OH)4
14.19.8HisingeriteFe23+(Si2O5)(OH)4 · 2H2O

Other Names for Fayalite

Name in Other Languages:
Dutch:Fayaliet
Italian:Fayalite
Lithuanian:Fajalitas
Polish:Fajalit
Portuguese:Faialite
Russian:Фаялит
Simplified Chinese:铁橄榄石

Other Information

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

References for Fayalite

Reference List:
Gmelin, C.G. (1840): Chemische Untersuchung des Fayalites, Annalen der Chemie und Physik, Vol. 127 (2/051), pp. 160

von Fellenberg, R.L. (1840): Analyse des Eisenperidots, eines neuen vulkanischen Minerals von den Azoren, Annalen der Physik und Chemie, Vol. 127 (2/051), pp. 261

Fisher G W, Medaris L G (1969) Cell dimensions and X-ray determinative curve for synthetic Mg-Fe olivines, American Mineralogist, 54, 741-753

Burns R G, Huggins F E (1972) Cation determinative curves for Mg-Fe-Mn olivines from vibrational spectra, American Mineralogist, 57, 967-985

Smyth J R (1975) High temperature crystal chemistry of fayalite, American Mineralogist, 60, 1092-1097

Hazen R M (1977) Effects of temperature and pressure on the crystal structure of ferromagnesian olivine, American Mineralogist, 62, 286-295

Schwab R G, Küstner D (1977) Präzisionsgitterkonstantenbestimmung zur Festlegung röntgenographischer Bestimmungskurven für synthetische Olivine der Mischkristallreihe Forsterit-Fayalit, Neues Jahrbuch für Mineralogie, Monatshefte, 5, 205-215

Riekel C, Weiss A (1978) Cation-ordering in synthetic Mg2-xFexSiO4-olivines, Zeitschrift für Naturforschung B Anorganische Chemie, Organische Chemie, 33b, 731-736

Fujino K, Sasaki S, Takéuchi Y, Sadanaga R (1981) X-ray determination of electron distributions in forsterite, fayalite and tephroite, Acta Crystallographica, B37, 513-518

O'Neill, H.St.C. (1987): The quartz-fayalite-magnetite equilibria and free energies of formation of fayalite (Fe2SiO4) and magnetite (Fe3O4). American Mineralogist: 72: 67-75.

Simon A. T. Redfern, K. S. Knight, C. M. B. Henderson, and B. J. Wood (1998):
Fe-Mn cation ordering in fayalite-tephroite (Fe x Mn (sub 1-x) ) 2 SiO 4 olivines; a neutron diffraction study. Mineralogical Magazine vol 62 pp 607-615.

Internet Links for Fayalite

Localities for Fayalite

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.
Mineral and/or Locality  
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