Fayalite Mineral Data

Fayalite Mineral Data +

[Content and History] [Recent Issues] [Back Issues] [Subscriptions] [Contacts]
See Also: [Diamond Crystals] [Excalibur Minerals] [Hudson Institute] [Minerals on CDROM]
Mineral News was founded some twenty years ago and has developed a following of
avid mineral collectors seeking timely information about new finds and other items
of interest to the collector community. Articles are solicited from collector and scientific authors.

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

Synonym:

Hortonolite - Mn,Mg

ICSD 26375

Knebelite(Mn)

PDF 31-633

Fayalite Image

Images:

Fayalite

Comments: Flattened crystals of fayalite on cristobalite.
Location: Coso Hot Springs, Inyo County, California. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

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

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

By Intensity(I/I_o): 2.831(1), 2.501(0.7), 2.566(0.5),

Crystal Structure:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
Keyboard
S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
P - Polyhedra On/Off
B - Bonds On/Off
Help on Above

Birle J D , Gibbs G V , Moore P B , Smith J V , American Mineralogist , 53 (1968) p.807-824, Crystal structures of natural olivines

View Additional jPOWD Structure files for Fayalite
[1] [10] [11] [2] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Fayalite

Cleavage:

[010] Indistinct

Color:

Brown, Black, Black.

Density:

4.39

Diaphaniety:

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:

None.

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

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:

r_electron=4.22 gm/cc
note: r_Fayalite=4.39 gm/cc.

Fermion Index

Fermion Index = 0.0182
Boson Index = 0.9818

Photoelectric:

PE_Fayalite= 17.09 barns/electron
U=PE_Fayalite x r_electron= 72.16 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Fayalite is Not Radioactive

Fayalite Classification

Dana Class:

51.3.1.1 (51)Nesosilicate Insular SiO4 Groups Only

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

(51.3.1)Olivine group

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

51.3.1.1 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m

51.3.1.2 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m

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

51.3.1.4 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m

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

Strunz Class:

VIII/A.04-20 VIII - Silicates

VIII/A - Nesosilicates with [SiO4]4-groups, cations of octahedral orientation [6]

VIII/A.04 - Olivine group

VIII/A.04-10 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m

VIII/A.04-20 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m

VIII/A.04-30 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m

VIII/A.04-40 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m

VIII/A.04-50 Laihunite FeFe2(SiO4)2 P 2₁/b 2/m

Other Fayalite Information

References:

NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

Search for Fayalite using:

[ALTAVISTA] [AOL] [About.com] [All-The-Web] [HotBot] [Ixquick] [LookSmart] [MAMMA] [MSN.COM] [Netscape] [Teoma] [Wikipedia] [YAHOO]

Visit our Advertisers for Fayalite :
AA Mineral Specimens
B and L Minerals
Dan Weinrich Fine Minerals
Dan Weinrich Auctions
e-Rocks Auctions
Excalibur Minerals
Exceptional Minerals
Fabre Minerals
Greenside Minerals
John Betts Fine Minerals
Masons Minerals
Minernet.it
Mineral News
Mineral of the Month Club
MineralsWeb Fine Minerals
Rockshop.cz Kalat Fine Minerals
T G Fine Minerals
Wrights Rock Shop

Translate Fayalite Mineral Data :

Ask about Fayalite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

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

Fayalite

Fe++2SiO4
Dana No: 51.3.1.1 Strunz No: VIII/A.04-20
Locality:

Notes: