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Epidote Group

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Allanite-(Y)
Eas a Bradain, Luib, Isle of Skye, North West Highlands (Inverness-shire), Scotland, UK
© Steve Rust

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Formula:
A
 
2
 M
 
3
(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Name:After the principal member of the group.


A group of monoclinic sorosilicates with the general formula given above.

A sites (A1, A2): large, high-coordination cations such as Ca, Sr or lanthanides
M sites (M1, M2, M3): octahedrally-coordinated, trivalent (occasionally divalent) cations such as Al3+, Fe3+, Mn3+, Fe2+ and Mg2+.

NOTE: Significant CNMMN-approved changes to the nomenclature and content of this group, with the establishment of 3 new sub-groups were published in 2006 (European Journal of Mineralogy, 18, 551-567). The nomenclature is based on the occupancy of the five A and M sites.

Classification of Epidote Group

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Chemical Properties of Epidote Group

Formula:
A
 
2
 M
 
3
(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)

Relationship of Epidote Group to other Species

Group Members:
Allanite-(Ce)
{CaCe}{Al
 
2
Fe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Allanite-(La)
{CaLa}{Al
 
2
Fe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Allanite-(Nd)
{CaNd}{Al
 
2
Fe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Allanite-(Y)
{CaY}{Al
 
2
Fe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Åskagenite-(Nd)
{Mn
2+
 
Nd}{Al
 
2
Fe
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O
 
2
Clinozoisite
{Ca
 
2
}{Al
 
3
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Clinozoisite-(Sr)
{CaSr}{Al
 
3
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Dissakisite-(Ce)
{CaCe}{Al
 
2
Mg}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Dissakisite-(La)
{CaLa}{Al
 
2
Mg}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Dollaseite-(Ce)
{CaCe}{MgAlMg}(Si
 
2
O
 
7
)(SiO
 
4
)(OH)F
Epidote
{Ca
 
2
}{Al
 
2
Fe
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Epidote-(Pb)
{CaPb}{Al
 
2
Fe
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Epidote-(Sr)
{CaSr}{Al
 
2
Fe
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Ferriallanite-(Ce)
{CaCe}{Fe
3+
 
AlFe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Ferriallanite-(La)
{CaLa}{Fe
3+
 
AlFe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Khristovite-(Ce)
{CaCe}{MgAlMn
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)(OH)F
Manganiandrosite-(Ce)
{(Mn
2+
 
,Ca)(Ce,REE)}{Mn
3+
 
AlMn
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Manganiandrosite-(La)
{LaMn
2+
 
}{Mn
3+
 
AlMn
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Manganipiemontite-(Sr)
{CaSr}{Mn
3+
 
AlMn
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Mukhinite
{Ca
 
2
}{Al
 
2
V
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Piemontite
{Ca
 
2
}{Al
 
2
Mn
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Piemontite-(Sr)
{CaSr}{Al
 
2
Mn
3+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Uedaite-(Ce)
{Mn
2+
 
Ce}{Al
 
2
Fe
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Unnamed (Ca-analogue of Manganiandrosite-(La))
{(Ca,(La,REE),Mn
2+
 
)
 
2
}{(Mn
3+
 
,Fe
3+
 
,Al)Al(Mn
2+
 
,Mg)}(Si
 
2
O
 
7
)((Si,Al,As)O
 
4
)O(OH)
Unnamed (Mg-analogue of Ferriallanite-(Ce))
{CaCe}{(Fe
3+
 
,Al)Al(Mg,Fe
2+
 
)}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Unnamed (Mn-analogue of Ferriallanite-(Ce))
{CaCe}{Fe
3+
 
AlMn
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Vanadoandrosite-(Ce)
{Mn
2+
 
Ce}{V
3+
 
AlMn
2+
 
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)
Zoisite
{Ca
 
2
}{Al
 
3
}(Si
 
2
O
 
7
)(SiO
 
4
)O(OH)

Other Information

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

References for Epidote Group

Reference List:

- +
Peacor, D.R. and Dunn, P.J. (1988) Dollaseite-(Ce)(magnesium orthite redefined): structure refinement and implications for F + M 2+ substitution in epidote-group minerals. American Mineralogist: 73: 838-842.

Gieré, R. and Sorensen, S.S. (2004) Allanite and other REE-rich epidote-group minerals. In: Epidotes (A. Liebscher & G. Franz, editors). Rev. Mineral. Geochem.: 56: 431-493.

Grapes, R.H. and Hoskin, W.O. (2004) Epidote Group Minerals in Low-Medium Pressure Metamorphic Terranes. Reviews in Mineralogy and Geochemistry: 56(1): 301-345.

Anthony, Edna B., Let's Talk Gemstones, Uncommon Sorosilicate Gemstones, part 3: The Epidote Group. The New Mexico Facetor.

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.

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    • Localities for Epidote Group

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