Pumpellyite

sorosilicate

pumpellyite facies

The pumpellyite group of minerals includes:
Pumpellyite-(Al): Ca2Al3(Si2O7)(SiO4)(OH,O)2.H2O
Pumpellyite-(Fe2+): Ca2Fe2+Al2(Si2O7)(SiO4) (OH,O)2.H2O
Pumpellyite-(Fe3+): Ca2(Fe3+,Mg)Al2(Si2O7)(SiO4) (OH,O)2.H2O
Pumpellyite-(Mg): Ca2MgAl2(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
Environments:

Metamorphic environments

Pumpellyite is characteristic of the prehnite-pumpellyite facies, and it is also a mineral of the blueschist facies.
Prehnite and pumpellyite form from calcium zeolites in the presence of calcite.

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