The pumpellyite group of minerals includes:
Pumpellyite-(Fe2+): Ca2Fe2+Al2(Si2O7)(SiO4) (OH,O)2.H2O
Pumpellyite-(Fe3+): Ca2(Fe3+,Mg)Al2(Si2O7)(SiO4) (OH,O)2.H2O
Pumpellyite-(Mn2+): Ca2Mn2+Al2(Si2O7)(SiO4) (OH,O)2.H2O
These are all sorosilicates (Si2O7 groups)
Hardness: Mg 5½
Streak: Mg white
Colour: Greenish black due to divalent iron Fe2+, green due to manganese Mg, blue, blackish green, brown, pale grey due to divalent manganese Mn2+, pink-brown
Pumpellyite is characteristic of the prehnite-pumpellyite
facies, and it is also a mineral of the blueschist facies.
Pumpellyite and prehnite form from calcium zeolites in the presence of calcite.
At Croft Quarry, Croft, Blaby, Leicestershire, England, UK, the prehnite-pumpellyite wall-rock alteration haloes that surround the zeolite - containing veins in the quartz - diorite contain pumpellyite-(Fe2+), associated with prehnite, chlorite, quartz and analcime, and also minor muscovite variety sericite, kaolinite and smectite (JRS 20.23).
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