Epidote group

Epidotes are a group of sorosilicate minerals that are common in igneous and metamorphic rocks.^[1][2][3]

Epidote group
General
Category	Sorosilicates
Formula	(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 [100]
Cleavage	{001} perfect and {100} imperfect
Mohs scale hardness	6–7
Luster	Vitreous

Epidote member species

• Clinozoisite, (CaCa)(AlAlAl)O[Si₂O₇][SiO₄](OH)
• Epidote, (CaCa)(AlAlFe³⁺)O[Si₂O₇][SiO₄](OH)
• Epidote-(Sr), (CaSr)(AlAlFe³⁺)O[Si₂O₇][SiO₄](OH)
• Hancockite, (CaPb)(AlAlFe³⁺)O[Si₂O₇][SiO₄](OH)
• Heflikite, (CaCa)(AlAlSc)O[Si₂O₇][SiO₄](OH)
• Mukhinite, (CaCa)(AlAlV³⁺)O[Si₂O₇][SiO₄](OH)
• Niigataite, (CaSr)(AlAlAl)O[Si₂O₇][SiO₄](OH)
• Piemontite, (CaCa)(AlAlMn³⁺)O[Si₂O₇][SiO₄](OH)
• Piemontite-(Pb), (CaPb)(AlAlMn³⁺)O[Si₂O₇][SiO₄](OH)
• Piemontite-(Sr), (CaSr)(AlAlMn³⁺)O[Si₂O₇][SiO₄](OH)
• Tweddillite, (CaSr)(Mn³⁺AlMn³⁺)O[Si₂O₇][SiO₄](OH)