Pumpellyite Subgroup

The pumpellyite subgroup 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)

The pumpellyite subgroup is a member of the pumpellyite group.

Environments:

Metamorphic environments

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 the Central No. 2 shaft, Central Mine, Central, Keweenaw county, Michigan, USA, a 1.49-mm needle of pumpellyite with a microsphere of hematite attached has been found in a void in conglomerate (R&M 97.4.357).

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