Forsterite Mineral Data

General Forsterite Information

Chemical Formula:

Mg2SiO4

Composition:

Molecular Weight = 140.69 gm

Magnesium 34.55 % Mg 57.29 % MgO

Silicon 19.96 % Si 42.71 % SiO₂

Oxygen 45.49 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mg₂(SiO₄)

Environment:

Ultramafic igneous rocks or dolomitic marbles.

IMA Status:

Valid Species (Pre-IMA) 1824

Locality:

Mte. Somma, Vesuvius, Italy. Link to MinDat.org Location Data.

Name Origin:

Named for Johann Forster, German naturalist.

Name Pronunciation:

Forsterite + Pronunciation

Synonym:

Chrysolite

ICSD 9334

Olivine

PDF 34-189

Peridot

Forsterite Image

Images:

Forsterite Olivine

Comments: Peridot (Forsterite) recrystallized at the base.
Location: Skardu, Nooristan, Pakistan. Scale: 2.5 x 2.7 cm.
© Fabre Minerals

Forsterite Crystallography

Axial Ratios:

a:b:c =0.4665:1:0.5866

Cell Dimensions:

a = 4.756, b = 10.195, c = 5.981, Z = 4; V = 290.00 Den(Calc)= 3.22

Crystal System:

Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: Pbnm

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.458(1), 2.512(0.7), 3.883(0.7),

Forms:

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Forms: ( 1 0 1) ( 1 0 0) ( 0 1 0) ( 1 1 0) ( 1 1 1) ( 0 0 1) ( 0 1 1)

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Physical Properties of Forsterite

Cleavage:

{001} Good, {010} Distinct

Color:

Colorless, Green, Yellow, Yellow green, White.

Density:

3.21 - 3.33, Average = 3.27

Diaphaneity:

Transparent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Crystalline - Fine - Occurs as well-formed fine sized crystals.

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

6-7 - Orthoclase-Quartz

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Forsterite

Gladstone-Dale:

CI meas= -0.051 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= -0.068 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2172,KPDmeas= 0.2139,KC= 0.2034
Ncalc = 1.65 - 1.68

Optical Data:

Biaxial (-), a=1.636-1.73, b=1.65-1.739, g=1.669-1.772, bire=0.0330-0.0420, 2V(Calc)=56-84, 2V(Meas)=74-90. Dispersion r > v or r < v.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Calculated Properties of Forsterite

Electron Density:

Bulk Density (Electron Density)=3.25 gm/cc
note: Specific Gravity of Forsterite =3.27 gm/cc.

Fermion Index:

Fermion Index = 0.04
Boson Index = 0.96

Photoelectric:

PE_Forsterite= 1.53 barns/electron
U=PE_Forsterite x rElectron Density= 4.98 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Forsterite is Not Radioactive

Forsterite Classification

Dana Class:

51.03.01.02 (51)Nesosilicate Insular SiO4 Groups Only

(51.03)with all cations in octahedral [6] coordination

(51.03.01)Olivine group

51.03.01.00 Olivine* (Mg,Fe)2SiO4 Pbnm 2/m 2/m 2/m

51.03.01.01 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m

51.03.01.02 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m

51.03.01.03 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m

51.03.01.04 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m

51.03.01.05 Laihunite FeFe2(SiO4)2 P 2₁/b 2/m

Strunz Class:

09.AC.05 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AC -Nesosilicates without additional anions;

09.AC.05 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m

09.AC.05 Glaucochroite CaMnSiO4 Pbnm 2/m 2/m 2/m

09.AC.05 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m

09.AC.05 Olivine* (Mg,Fe)2SiO4 Pbnm 2/m 2/m 2/m

09.AC.05 Kirschsteinite CaFeSiO4 Pbmn 2/m 2/m 2/m

09.AC.05 Laihunite FeFe2(SiO4)2 P 2₁/b 2/m

09.AC.05 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m

09.AC.05 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m

Other Forsterite Information

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Print or Cut-and-Paste your Forsterite Specimen Label here :

Forsterite

Mg2SiO4
Dana No: 51.03.01.02 Strunz No: 09.AC.05
Locality:

Notes:

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