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Epidote

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Formula:
{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Colour:
Yellowish-green, green, brownish-green, black
Lustre:
Vitreous, Pearly
Hardness:
6
Specific Gravity:
3.38 - 3.49
Crystal System:
Monoclinic
Name:
Named in 1801 by Rene Just Haüy from the Greek επιδοσιζ ("epidosis"), meaning "increase", in allusion to the crystal characteristic of one longer side at the base of the prism.
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Classification of EpidoteHide

Approved, 'Grandfathered' (first described prior to 1959)
9.BG.05a

9 : SILICATES (Germanates)
B : Sorosilicates
G : Sorosilicates with mixed SiO4 and Si2O7 groups; cations in octahedral [6] and greater coordination
58.2.1a.7

58 : SOROSILICATES Insular, Mixed, Single, and Larger Tetrahedral Groups
2 : Insular, Mixed, Single, and Larger Tetrahedral Groups with cations in [6] and higher coordination; single and double groups (n = 1, 2)
16.21.2

16 : Silicates Containing Aluminum and other Metals
21 : Aluminosilicates of Fe and Ca

Pronounciation of EpidoteHide

Pronounciation:
PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Physical Properties of EpidoteHide

Vitreous, Pearly
Transparency:
Transparent, Opaque
Colour:
Yellowish-green, green, brownish-green, black
Streak:
Colourless
Hardness:
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {001}, imperfect on {100}
Fracture:
Irregular/Uneven
Density:
3.38 - 3.49 g/cm3 (Measured)    3.43(3) g/cm3 (Calculated)

Optical Data of EpidoteHide

Type:
Biaxial (-)
RI values:
nα = 1.715 - 1.751 nβ = 1.725 - 1.784 nγ = 1.734 - 1.797
2V:
Measured: 90° to 116°, Calculated: 62° to 84°
Max Birefringence:
δ = 0.019 - 0.046
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
strong r > v
Pleochroism:
Strong
Comments:
X= colourless, pale yellow, pale green
Y= greenish yellow
Z= yellowish green

Chemical Properties of EpidoteHide

Formula:
{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
IMA Formula:
Ca2Fe3+Al2(Si2O7)(SiO4)O(OH)
Common Impurities:
Al,Mg,Mn

Crystallography of EpidoteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/m
Cell Parameters:
a = 8.8877(14) Å, b = 5.6275(8) Å, c = 10.1517(12) Å
β = 115.383(14)°
Ratio:
a:b:c = 1.579 : 1 : 1.804
Unit Cell V:
458.73 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals prismatic to 35 cm. Fibrous, coarse to finely granular, massive.
Twinning:
On {100}, contact, lamellar, common.

Crystallographic forms of EpidoteHide

Crystal Atlas:
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Epidote no.9 - Goldschmidt (1913-1926)
Epidote no.94 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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X-Ray Powder DiffractionHide

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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Type Occurrence of EpidoteHide

Synonyms of EpidoteHide

Other Language Names for EpidoteHide

Varieties of EpidoteHide

Allanite-EpidoteEpidote enriched with REE and Y transitive to allanite. Its REE+Y content is below 0.5 apfu. Sometimes such epidotes able to be selectively enriched with Eu (as it is on Tsakhirin Khuduk deposit in Mongolian Altai).
Beryllian EpidoteA beryllium-bearing variety of epidote.
Chrome-PistaziteA chromian Epidote with Fe3+>Al
RosstrevoriteA fibrous stellate variety of Epidote, from Rosstrevor, Co.Down, Ireland.
(Greg and Lettsom, 1858)
TawmawiteA Cr-bearing epidote.
WithamiteA Mn-rich variety of Epidote.
Originally reported from Glen Coe, Strathclyde (Argyllshire), Scotland, UK.
YttroepidoteYttrian Epidote with Y+REE content below 0.5 apfu. Transitive to Allanite-(Y).
First described from Slyudorudnik locality at Southern Ural in 1959.

Relationship of Epidote to other SpeciesHide

Other Members of this group:
Clinozoisite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
Epidote-(Sr){CaSr}{Al2Fe3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
Hancockite{CaPb}{Al2Fe3+}(Si2O7)(SiO4)O(OH)Mon.
Mukhinite{Ca2}{Al2V3+}(Si2O7)(SiO4)O(OH)Mon.
Niigataite{CaSr}{Al3}(Si2O7)(SiO4)O(OH)Mon. 2/m
Piemontite{Ca2}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
Piemontite-(Pb){CaPb}{Al2Mn3+}(Si2O7)(SiO4)O(OH) Mon. 2/m : P21/m
Piemontite-(Sr){CaSr}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon.
Tweddillite{CaSr}{Mn3+AlMn3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
Group Members:
Pistacite {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Unnamed (Ga-dominant member of the epidote group) {Ca2}{Al2(Ga,Fe)}(Si2O7)(SiO4)O(OH)

Related Minerals - Nickel-Strunz GroupingHide

9.BG.XCyprineCa19Cu2+(Al10Mg2)Si18O68(OH)10Tet. 4/m : P4/n
9.BG.05bAllanite-(Ce){CaCe}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bAllanite-(La){CaLa}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bAllanite-(Y){CaY}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon.
9.BG.05aClinozoisite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bDissakisite-(Ce){CaCe}{Al2Mg}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Dollaseite-(Ce){CaCe}{MgAlMg}(Si2O7)(SiO4)(OH)FMon. 2/m : P21/m
9.BG.05Hancockite{CaPb}{Al2Fe3+}(Si2O7)(SiO4)O(OH)Mon.
9.BG.05Khristovite-(Ce){CaCe}{MgAlMn2+}(Si2O7)(SiO4)(OH)FMon.
9.BG.05Mukhinite{Ca2}{Al2V3+}(Si2O7)(SiO4)O(OH)Mon.
9.BG.05Piemontite{Ca2}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Piemontite-(Sr){CaSr}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon.
9.BG.05bManganiandrosite-(La){Mn2+La}{Mn3+AlMn2+}(Si2O7)(SiO4)O(OH)Mon.
9.BG.05Tawmawite{Ca2}{(Al,Fe3+,Cr)3}(Si2O7)(SiO4)O(OH)
9.BG.05Tweddillite{CaSr}{Mn3+AlMn3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bFerriallanite-(Ce){CaCe}{Fe3+AlFe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Niigataite{CaSr}{Al3}(Si2O7)(SiO4)O(OH)Mon. 2/m
9.BG.05Manganiandrosite-(Ce){Mn2+Ce}{Mn3+AlMn2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Dissakisite-(La){CaLa}{Al2Mg}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Vanadoandrosite-(Ce){Mn2+Ce}{V3+AlMn2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Uedaite-(Ce){Mn2+Ce}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05Epidote-(Sr){CaSr}{Al2Fe3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bAllanite-(Nd){CaNd}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bFerriallanite-(La){CaLa}{Fe3+AlFe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
9.BG.05bÅskagenite-(Nd){Mn2+Nd}{Al2Fe3+}(Si2O7)(SiO4)O2Mon. 2/m : P21/m
9.BG.10Zoisite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)Orth. mmm (2/m 2/m 2/m) : Pnma
9.BG.15MacfalliteCa2Mn3+3(SiO4)(Si2O7)(OH)3Mon.
9.BG.15SursassiteMn2+2Al3(SiO4)(Si2O7)(OH)3Mon. 2/m : P21/m
9.BG.20Julgoldite-(Fe2+)Ca2Fe2+Fe3+2(Si2O7)(SiO4)(OH)2 · H2OMon.
9.BG.20OkhotskiteCa2(Mn,Mg)(Mn3+,Al,Fe3+)2(Si2O7)(SiO4)(OH)2 · H2OMon.
9.BG.20Pumpellyite-(Fe2+)Ca2Fe2+Al2(Si2O7)(SiO4)(OH)2 · H2OMon.
9.BG.20Pumpellyite-(Fe3+)Ca2(Fe3+,Mg)(Al,Fe3+)2(Si2O7)(SiO4)(OH,O)2 · H2OMon.
9.BG.20Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2OMon.
9.BG.20Pumpellyite-(Mn2+)Ca2Mn2+Al2(Si2O7)(SiO4)(OH)2 · H2OMon.
9.BG.20ShuiskiteCa2MgCr2(Si2O7)(SiO4)(OH)2 · 2H2OMon.
9.BG.20Julgoldite-(Fe3+)Ca2Fe3+Fe3+2(Si2O7)(SiO4)O(OH) · H2OMon.
9.BG.20Pumpellyite-(Al)Ca2Al3(Si2O7)(SiO4)(OH,O)2 · H2OMon.
9.BG.20PoppiiteCa2(V3+,Fe3+,Mg)(V3+,Al)2(Si2O7)(SiO4)(OH,O)2 · H2OMon. 2/m : B2/m
9.BG.20Julgoldite-(Mg)Ca2MgFe3+2(Si2O7)(SiO4)(OH)2 · H2OMon.
9.BG.25GanomalitePb9Ca5Mn(Si2O7)4(SiO4)OHex.
9.BG.30RustumiteCa10(Si2O7)2(SiO4)(OH)2Cl2Mon.
9.BG.35Vesuvianite(Ca,Na,☐)19(Al,Mg,Fe3+)13(☐,B,Al,Fe3+)5(Si2O7)4(SiO4)10(OH,F,O)10Tet.
9.BG.35WiluiteCa19(Al,Mg)13(B,☐,Al)5(Si2O7)4(SiO4)10(O,OH)10Tet. 4/mmm (4/m 2/m 2/m) : P4/nnc
9.BG.35ManganvesuvianiteCa19Mn3+(Al,Mn3+,Fe3+)10(Mg,Mn2+)2(Si2O7)4(SiO4)10O(OH)9Tet. 4/m : P4/n
9.BG.35FluorvesuvianiteCa19(Al,Mg,Fe2+)13(Si2O7)4(SiO4)10O(F,OH)9Tet. 4/mmm (4/m 2/m 2/m)
9.BG.40Vyuntspakhkite-(Y)(Y,Yb)4Al2.5-1.5(Si,Al)1.5-2.5(SiO4)4O(OH)7
9.BG.45DellaiteCa6Si3O11(OH)2Tric.
9.BG.50Gatelite-(Ce)CaCe3Al2(Al,Mg)(Mg,Fe2+,Al)(Si2O7)(SiO4)3(O,F)(OH,O)2Mon. 2/m : P21/b
9.BG.55Västmanlandite-(Ce)Ce3CaMg2Al2Si2O15(OH)2FMon. 2/m : P21/m

Related Minerals - Dana Grouping (8th Ed.)Hide

58.2.1a.1Allanite-(Ce){CaCe}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
58.2.1a.2Allanite-(La){CaLa}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
58.2.1a.3Allanite-(Y){CaY}{Al2Fe2+}(Si2O7)(SiO4)O(OH)Mon.
58.2.1a.4Clinozoisite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
58.2.1a.5Dissakisite-(Ce){CaCe}{Al2Mg}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
58.2.1a.6Dollaseite-(Ce){CaCe}{MgAlMg}(Si2O7)(SiO4)(OH)FMon. 2/m : P21/m
58.2.1a.8Hancockite{CaPb}{Al2Fe3+}(Si2O7)(SiO4)O(OH)Mon.
58.2.1a.9Khristovite-(Ce){CaCe}{MgAlMn2+}(Si2O7)(SiO4)(OH)FMon.
58.2.1a.10Mukhinite{Ca2}{Al2V3+}(Si2O7)(SiO4)O(OH)Mon.
58.2.1a.11Piemontite{Ca2}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
58.2.1a.12Piemontite-(Sr){CaSr}{Al2Mn3+}(Si2O7)(SiO4)O(OH)Mon.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

16.21.1EsseneiteCaFe3+[AlSiO6]Mon. 2/m : B2/b
16.21.3Ferro-tschermakite☐{Ca2}{Fe2+3Al2}(Al2Si6O22)(OH)2Mon. 2/m : B2/m
16.21.4Ferro-aluminotschermakite☐{Ca2}{Fe2+3Al2}(Al2Si6O22)(OH)2Mon.
16.21.5Ferri-tschermakite☐{Ca2}{Mg3Fe3+2}(Al2Si6O22)(OH)2Mon.
16.21.6Ferro-Ferri-tschermakite☐{Ca2}{Fe2+3Fe3+2}(Al2Si6O22)(OH)2Mon.
16.21.7Alumino-ferro-hornblende☐{Ca2}{Fe2+4Al}(AlSi7O22)(OH)2
16.21.8Pumpellyite-(Fe2+)Ca2Fe2+Al2(Si2O7)(SiO4)(OH)2 · H2OMon.
16.21.8Pumpellyite-(Fe3+)Ca2(Fe3+,Mg)(Al,Fe3+)2(Si2O7)(SiO4)(OH,O)2 · H2OMon.

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Epidote in petrologyHide

References for EpidoteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Dana, E.S. (1892) Dana's system of mineralogy, 6th. edition. New York: 516-521.
Gottardi G. (1954) Dati ed osservazioni sulla struttura dell'epidoto. Periodico di Mineralogia: 245-250.
Seki, Y. (1959) Relation between chemical composition and lattice constants of epidote. American Mineralogist: 44: 720-730.
Chatterjee, N.D. (1962) Vesuvianite-epidote paragenesis as a product of greenschist facies of regional metamorphism in the Western Alps. Beiträge zur Mineralogie und Petrographie: 8: 432-439.
Keith, T.E.C., Muffler L.J.P., Cremer, M. (1968) Hydrothermal epidote formed in the Salton Sea geothermal system, California. American Mineralogist: 53: 1635-1644.
Dollase, W.A. (1971) Refinement of the crystal structures of epidote, allanite and hancockite. American Mineralogist: 56: 447-464.
Gabe, E.J., Portheine, J.C., Whitlow, S.H. (1973) A reinvestigation of the epidote structure: confirmation of the iron location. American Mineralogist: 58: 218-223.
Sakai, C., Higashino, T., Enami, M. (1984) REE-bearing epidote from Sanbagawa pelitic schists, central Shikoku, Japan. Geochemical Journal: 18: 45-53.
Deer, W.A., Howie, R.A., Zussman, J. (1986) Rock-forming minerals, (2nd edition), v. 1B, disilicates and ring silicates: 44: 134.
Kvick, Å, Pluth, J.J., Richardson, J.W. Jr., Smith, J.V. (1988) The ferric iron distribution and hydrogen bonding in epidote: a neutron diffraction study at 15 K. Acta Crystallographica: 44: 351-355.
Holland, T.J.B., Redfern, S.A.T., Pawley, A.R. (1996) Volume behavior of hydrous minerals at high pressure and temperature: II. Compressibilities of lawsonite, zoisite, clinozoisite and epidote. American Mineralogist: 81: 341-348.
Gieré, R., Sorensen, S.S. (2004) Allanite and other REE-rich epidote-group minerals. In: Epidotes (A. Liebscher & G. Franz, editors). Reviews in Mineralogy and Geochemistry: 56: 431-493.
Armbruster, T., Bonazzi, P., Akasaka, M., Bermanec, V., Chopin, C., Gieré R., Heuss-Assbichler, S., Liebscher, A., Menchetti, S., Pan, Y., Pasero, M. (2006) Recommended nomenclature of epidote-group minerals. European Journal of Mineralogy: 18: 551-567.

Internet Links for EpidoteHide

Localities for EpidoteHide

This 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.

Locality ListShow