Mineralogy Database

Omphacite Mineral Data

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General Omphacite Information

Help on Chemical  Formula: Chemical Formula: (Ca,Na)(Mg,Fe++,Al)Si2O6
Help on Composition: Composition: Molecular Weight = 211.37 gm
   Sodium      3.26 %  Na    4.40 % Na2O
   Calcium    11.38 %  Ca   15.92 % CaO
   Magnesium   6.90 %  Mg   11.44 % MgO
   Aluminum    3.83 %  Al    7.24 % Al2O3
   Iron        2.64 %  Fe    3.40 % FeO
   Silicon    26.57 %  Si   56.85 % SiO2
   Oxygen     45.42 %  O
             ______        ______ 
             100.00 %       99.24 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Ca0.6Na0.3Mg0.6Al0.3Fe2+0.1Si2O6
Help on Environment: Environment: Major constituent of eclogite, commonly in kimberlite pipes; from some ophiolites and glaucophane-bearing blueschist facies rocks.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1815
Help on Locality: Locality: Tiburon Pininsula, Marin County, and Sonoma County, California, USA. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: From the Greek for "unripe grapes", in allusion to its green color.
Help on Name Pronunciation: Name Pronunciation: Omphacite + Pronunciation Say OMPHACITE
Help on Synonym: Synonym: ICSD 63236
  PDF 42-568

Omphacite Image

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Comments: Dark green crystalline omphacite with glaucophane.
Location: Healdsburg, Sonoma County, California, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Omphacite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =1.0921:1:0.5993
Help on Cell Dimensions: Cell Dimensions: a = 9.585, b = 8.776, c = 5.26, Z = 4; beta = 106.85° V = 423.46 Den(Calc)= 3.32
Help on Crystal System: Crystal System: Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 2/n
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 2.98(1), 1.4(0.8), 2.13(0.7),

Physical Properties of Omphacite

Help on Cleavage: Cleavage: {110} Good, {110} Good
Help on Color: Color: Grass green, Dark green.
Help on Density: Density: 3.29 - 3.39, Average = 3.34
Help on Diaphaneity: Diaphaneity: Translucent
Help on Fracture: Fracture: Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.
Help on Habit: Habit: Anhedral Grains - Granular minerals without the expression of crystal shapes
Help on Habit: Habit: Massive - Granular - Common texture observed in granite and other igneous rock.
Help on Hardness: Hardness: 5-6 - Between Apatite and Orthoclase
Help on Luster: Luster: Vitreous - Silky
Help on Streak: Streak: greenish white

Optical Properties of Omphacite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= -0.014 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.021 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2085,KPDmeas= 0.2072,KC= 0.2043
Ncalc = 1.67 - 1.69
Help on Optical Data: Optical Data: Biaxial (+), a=1.662-1.701, b=1.67-1.712, g=1.685-1.723, bire=0.0220-0.0230, 2V(Calc)=74-88, 2V(Meas)=58-83. Dispersion r > v moderate.
Help on Pleochroism (x): Pleochroism (x): colorless.
Help on Pleochroism (y): Pleochroism (y): very pale green.
Help on Pleochroism (z): Pleochroism (z): very pale greenish blue or very pale green.

Calculated Properties of Omphacite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=3.32 gm/cc
note: Specific Gravity of Omphacite =3.34 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.02
Boson Index = 0.98
Help on Photoelectric: Photoelectric: PEOmphacite = 3.51 barns/electron
U=PEOmphacite x rElectron Density= 11.66 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Omphacite is Not Radioactive

Omphacite Classification

Help on  Dana Class: Dana Class: 65.01.03b.01 (65)Inosilicate Single-Width Unbranched Chains, W=1
  (65.01)with chains P=2
  (65.01.03b)C2/c clinopyroxenes (intermediate clinopyroxenes)
65.01.03b.01 Omphacite (Ca,Na)(Mg,Fe,Al)Si2O6 P 2/n 2/m
65.01.03b.02 Aegirine-augite* (Ca,Na)(Mg,Fe,Fe)[Si2O6] C 2/c 2/m
Help on  Strunz Class: Strunz Class: 09.DA.20 09 - SILICATES (Germanates)
  09.D - Inosilicates* Structural terminology according to Liebau (1985)
  09.DA -Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
09.DA.20 Aegirine-augite* (Ca,Na)(Mg,Fe,Fe)[Si2O6] C 2/c 2/m
09.DA.20 Omphacite (Ca,Na)(Mg,Fe,Al)Si2O6 P 2/n 2/m

Other Omphacite Information

Help on References: References: NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic2)
Help on See Also: See Also: Links to other databases for Omphacite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineral and Gemstone Kingdom
12 - Mineralienatlas (Deutsch)
13 - Online Mineral Museum
14 - QUT Mineral Atlas
15 - Ruff.Info

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Dana No: 65.01.03b.01 Strunz No: 09.DA.20





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