Fayalite Mineral Data
General Fayalite Information
Chemical Formula:
Fe++2SiO4
Composition:
Molecular Weight = 203.78 gm
Iron 54.81 % Fe 70.51 % FeO
Silicon 13.78 % Si 29.49 % SiO2
Oxygen 31.41 % O
______ ______
100.00 % 100.00 % = TOTAL OXIDE
Empirical Formula:
Fe2+2(SiO4)
Environment:
Ultra mafic silica-poor igneous rocks.
IMA Status:
Valid Species (Pre-IMA) 1840
Locality:
Fayal Island, Azores Link to MinDat.org Location Data.
Name Origin:
Named for the locality
Name Pronunciation:
Fayalite 
Synonym:
Hortonolite - Mn,Mg
ICSD 26375
Knebelite(Mn)
PDF 31-633
Fayalite Image
Images:
Fayalite Crystallography
Axial Ratios:
a:b:c =0.4666:1:0.5862
Cell Dimensions:
a = 4.76, b = 10.2, c = 5.98, Z = 4; V = 290.34 Den(Calc)= 4.66
Crystal System:
Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: Pbnm
X Ray Diffraction:
By Intensity(I/Io): 2.831(1), 2.501(0.7), 2.566(0.5),
Crystal Structure:
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Physical Properties of Fayalite
Cleavage:
{010} Indistinct
Color:
Brown, Black, Black.
Density:
4.39
Diaphaneity:
Transparent to Translucent
Fracture:
Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit:
Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Habit:
Massive - Granular - Common texture observed in granite and other igneous rock.
Hardness:
6.5 - Pyrite
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Fayalite
Gladstone-Dale:
CI meas= 0.055 (Good) - where the CI = (1-KPDmeas/KC)CI calc= 0.11 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1726,KPDmeas= 0.1833,KC= 0.1939
Ncalc = 1.85 - 1.9
Optical Data:
Biaxial (-), a=1.731-1.824, b=1.76-1.864, g=1.773-1.875, bire=0.0420-0.0510, 2V(Calc)=54-66, 2V(Meas)=74-47. Dispersion weak, r > v.
Pleochroism (x):
greenish yellow, pale yellow, or pale amber.
Pleochroism (y):
orange yellow, orange yellow, or orange yellow.
Pleochroism (z):
greenish yellow, pale yellow, or pale amber.
Calculated Properties of Fayalite
Electron Density:
Bulk Density (Electron Density)=4.22 gm/ccnote: Specific Gravity of Fayalite =4.39 gm/cc.
Fermion Index:
Fermion Index = 0.01Boson Index = 0.99
Photoelectric:
PEFayalite = 17.09 barns/electronU=PEFayalite x rElectron Density= 72.16 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units)Fayalite is Not Radioactive
Fayalite Classification
Dana Class:
51.03.01.01 (51)Nesosilicate Insular SiO4 Groups Only
(51.03)with all cations in octahedral [6] coordination
(51.03.01)Olivine group
Strunz Class:
09.AC.05 09 - SILICATES (Germanates)
09.A - Nesosilicates
09.AC -Nesosilicates without additional anions;
Other Fayalite Information
References:
NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)
See Also:
Links to other databases for Fayalite :1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - CalTech Mineral Spectroscopy
5 - EUROmin Project
6 - Ecole des Mines de Paris
7 - Franklin Minerals(Dunn)
8 - GeoScienceWorld
9 - Google Images
10 - Google Scholar
11 - Handbook of Mineralogy (MinSocAm)
12 - Handbook of Mineralogy (UofA)
13 - MinDAT
14 - Mineralienatlas (Deutsch)
15 - Online Mineral Museum
16 - QUT Mineral Atlas
17 - Ruff.Info
18 - UCLA - Petrography Thin-Sections
19 - University of Colorado - Mineral Structure Data
20 - University of Texas at Austin
21 - WWW-MINCRYST
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Ask about Fayalite here :
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Print or Cut-and-Paste your Fayalite Specimen Label here :
Fayalite
Fe++2SiO4Dana No: 51.03.01.01 Strunz No: 09.AC.05
Locality:
Notes: