| Epidote group | |
|---|---|
 | |
| General | |
| Category | Sorosilicates |
| Formula (repeating unit) | (A2+1A2+2)(M3+1M3+2M3+3)O[Si2O7][SiO4](OH) |
| IMA symbol | Ep |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H–M symbol) |
| Space group | P21/m |
| Identification | |
| Color | Yellow-green, pistachio green, greenish black, brownish-green, green, black |
| Crystal habit | Prismatic, fibrous, druse/encrustation, massive |
| Twinning | On |
| Cleavage | {001} perfect and {100} imperfect |
| Mohs scale hardness | 6–7 |
| Luster | Vitreous |
Epidotes are a group of sorosilicate minerals that are common in igneous and metamorphic rocks.
Epidote member species
- Clinozoisite, (CaCa)(AlAlAl)O[Si2O7][SiO4](OH)
- Epidote, (CaCa)(AlAlFe)O[Si2O7][SiO4](OH)
- Epidote-(Sr), (CaSr)(AlAlFe)O[Si2O7][SiO4](OH)
- Hancockite, (CaPb)(AlAlFe)O[Si2O7][SiO4](OH)
- Heflikite, (CaCa)(AlAlSc)O[Si2O7][SiO4](OH)
- Mukhinite, (CaCa)(AlAlV)O[Si2O7][SiO4](OH)
- Niigataite, (CaSr)(AlAlAl)O[Si2O7][SiO4](OH)
- Piemontite, (CaCa)(AlAlMn)O[Si2O7][SiO4](OH)
- Piemontite-(Pb), (CaPb)(AlAlMn)O[Si2O7][SiO4](OH)
- Piemontite-(Sr), (CaSr)(AlAlMn)O[Si2O7][SiO4](OH)
- Tweddillite, (CaSr)(MnAlMn)O[Si2O7][SiO4](OH)
References
- 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 (5): 551−567. Bibcode:2006EJMin..18..551A. doi:10.1127/0935-1221/2006/0018-0551.
- Kartashov, P. M. (2014). "Classification diagram for REE-bearing members of the epidote group based on crystallochemical data". Proceedings of the Workshop on Acessory Minerals: 25−26.
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.