Help mindat.org|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on MindatThe Mindat Store
Minerals by PropertiesMinerals by ChemistryRandom MineralSearch by minIDLocalities Near MeSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportAdd Glossary Item
StatisticsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

Omphacite

This page is currently not sponsored. Click here to sponsor this page.
Formula:
(Ca,Na)(Mg,Al)Si2O6
System:
Monoclinic
Colour:
dark green
Hardness:
5 - 6
Name:
From the Greek for unripe grape, in allusion to its green colour.
Pyroxene Group.
A clinopyroxene solid solution of jadeite (25%-75%), augite (25%-75%), and aegirine (0%-25%).
Retained as a distinct species for practical reasons.

A primary constituent of the rock eclogite.

Visit gemdat.org for gemological information about Omphacite.

Classification of Omphacite

Approved
8/F.01-100
9.DA.20

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
65.1.3b.1

65 : INOSILICATES Single-Width,Unbranched Chains,(W=1)
1 : Single-Width Unbranched Chains, W=1 with chains P=2
16.24.2

16 : Silicates Containing Aluminum and other Metals
24 : Aluminosilicates of Fe, Mg, Ca and alkalis
mindat.org URL:
http://www.mindat.org/min-2991.html
Please feel free to link to this page.

First Recorded Occurrence of Omphacite

Year of Discovery:
1815

Physical Properties of Omphacite

Colour:
dark green
Streak:
greenish white
Hardness (Mohs):
5 - 6
Cleavage:
Distinct/Good

Crystallography of Omphacite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 9.66Å, b = 8.81Å, c = 5.22Å
β = 106.56°
Ratio:
a:b:c = 1.096 : 1 : 0.593
Unit Cell Volume:
V 425.82 ų (Calculated from Unit Cell)
Comment:
Space group may be C2/c or P2/n.

Optical Data of Omphacite

Type:
Biaxial (+)
RI values:
nα = 1.662 - 1.701 nβ = 1.670 - 1.712 nγ = 1.685 - 1.723
2V:
Measured: 58° to 83°, Calculated: 74° to 88°
Max Birefringence:
δ = 0.023
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r > v moderate

Chemical Properties of Omphacite

Formula:
(Ca,Na)(Mg,Al)Si2O6
Essential elements:
All elements listed in formula:
Common Impurities:
Ti,Cr,Mn,K,H2O

Relationship of Omphacite to other Species

Other Members of Group:
AegirineNaFe3+Si2O6
Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
Augite(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
ClinoenstatiteMgSiO3
ClinoferrosiliteFe2+SiO3
DiopsideCaMgSi2O6
EsseneiteCaFe3+[AlSiO6]
GrossmaniteCaTi3+ AlSiO6
HedenbergiteCaFe2+Si2O6
JadeiteNa(Al,Fe3+)Si2O6
Jervisite(Na,Ca,Fe2+)(Sc,Mg,Fe2+)Si2O6
JohannseniteCaMn2+Si2O6
KanoiteMn2+(Mg,Mn2+)Si2O6
KosmochlorNaCrSi2O6
KushiroiteCaAl[AlSiO6]
NamansiliteNaMn3+Si2O6
NatalyiteNa(V3+,Cr)Si2O6
PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6
Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6
SpodumeneLiAlSi2O6
9.DA.05Donpeacorite(Mn2+,Mg)Mg[SiO3]2
9.DA.05EnstatiteMgSiO3
9.DA.05FerrosiliteFeSiO3
9.DA.10ClinoenstatiteMgSiO3
9.DA.10ClinoferrosiliteFe2+SiO3
9.DA.10KanoiteMn2+(Mg,Mn2+)Si2O6
9.DA.10Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6
9.DA.15Augite(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
9.DA.15DiopsideCaMgSi2O6
9.DA.15EsseneiteCaFe3+[AlSiO6]
9.DA.15HedenbergiteCaFe2+Si2O6
9.DA.15JohannseniteCaMn2+Si2O6
9.DA.15PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6
9.DA.15DavisiteCaScAlSiO6
9.DA.15KushiroiteCaAl[AlSiO6]
9.DA.15GrossmaniteCaTi3+ AlSiO6
9.DA.20Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
9.DA.25AegirineNaFe3+Si2O6
9.DA.25JadeiteNa(Al,Fe3+)Si2O6
9.DA.25Jervisite(Na,Ca,Fe2+)(Sc,Mg,Fe2+)Si2O6
9.DA.25KosmochlorNaCrSi2O6
9.DA.25NamansiliteNaMn3+Si2O6
9.DA.25NatalyiteNa(V3+,Cr)Si2O6
9.DA.30SpodumeneLiAlSi2O6
16.24.1Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
16.24.4Ferri-katophoriteNa(CaNa)(Mg4Fe3+)(AlSi7O22)(OH)2
16.24.5Ferro-ferri-katophoriteNaCaNaFe42+(Fe3+)[(AlSi7)O22](OH)2
16.24.6Barroisite☐{CaNa}{Mg3Al2}(AlSi7O22)(OH)2
16.24.7Ferri-barroisite☐(CaNa)(Mg3Fe23+)(AlSi7O22)(OH)2
16.24.8Alumino-ferrobarroisite☐{CaNa}{Fe32+Al2}(AlSi7O22)(OH)2
16.24.9Ferro-barroisite☐{CaNa}{Fe32+Al2}(AlSi7O22)(OH)2
16.24.10Ferro-ferri-barroisite☐(CaNa)(Fe32+Fe23+)(AlSi7O22)(OH)2
16.24.11Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
16.24.12Magnesio-hastingsite{Na}{Ca2}{Mg4Fe3+}(Al2Si6O22)(OH)2
16.24.13Taramite Root NameA(CaNa)(Z32+Z23+)(Al2Si6O22)(OH,F,Cl)2
16.24.14Ferri-taramiteNa(CaNa)(Mg3Fe23+)(Al2Si6O22)(OH)2
16.24.15Magnesiotaramite{Na}{CaNa}{Mg3AlFe3+}(Al2Si6O22)(OH)2
16.24.16Osumilite-(Mg)KMg2Al3(Al2Si10)O30
16.24.16Osumilite(K,Na)(Fe2+,Mg)2(Al,Fe3+)3(Si,Al)12O30

Other Names for Omphacite

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 Omphacite

Reference List:
Clark, Joan R. & J.J. Papike (1968), Crystal chemistry characterization of omphacites: American Mineralogist: 53: 840-868.

Clark, Joan R. & J.J. Papike (1969), Cation distribution in the crystal structure of omphacite, the eclogitic pyroxene: Geological Society of America Abstract for 1968.

Edgar, A.D., A. Mottana & N.D. MacRae (1969), The chemistry and cell parameters of omphacite and related pyroxenes: Mineralogical Magazine: 37: 61-74.

Champness, P.E. (1973), Speculation on an order-disorder transformation in omphacite: American Mineralogist: 58: 540-542.

Aldridge, L.P., Bancroft, G.M., Fleet, M.E., and Herzberg, C.T. (1978): Omphacite studies. II. Mössbauer spectra of C2/c and P2/n omphacites. American Mineralogist: 63: 1107-1115.

A. Mottana, G. Rossi, A. Kracher, G. Kurat (1979): Violan revisited: Mn-bearing omphacite and diopside. Tschermaks mineralogische und petrographische Mitteilungen 26, 187-201.

European Journal of Mineralogy (1998): 10: 889.

Katerinopoulou, A.; Katerinopoulos, A.; Bieniok, A.; Knop, E.; Magganas, A.; Amthauer, G. (2007): Crystal chemistry, structure analyses and phase transition experiment on an omphacite from eclogitic metagabbro from Syros island, Greece. Mineralogy and Petrology 91, 117-128.

Internet Links for Omphacite

Localities for Omphacite

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  
Copyright © mindat.org 1993-2015, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: January 31, 2015 10:16:28 Page generated: January 23, 2015 18:25:49