Pumpellyite


Pumpellyite is a group of closely related sorosilicate minerals:
  • pumpellyite-:
  • pumpellyite-:
  • pumpellyite-:
  • pumpellyite-:
  • pumpellyite-:
Pumpellyite crystallizes in the monoclinic-prismatic crystal system. It typically occurs as blue-green to olive green fibrous to lamellar masses. It is translucent and glassy with a Mohs hardness of 5.5 and a specific gravity of 3.2. It has refractive indices of nα=1.674–1.748, nβ=1.675–1.754 and nγ=1.688–1.764.
Pumpellyite occurs as amygdaloidal and fracture fillings in basaltic and gabbroic rocks in metamorphic terranes. It is an indicator mineral of the [Prehnite-pumpellyite facies|prehnite-pumpellyite metamorphic facies]. It is associated with chlorite, epidote, quartz, calcite and prehnite.
It was first described in 1925 for occurrences in the Calumet mine, Houghton [County, Michigan|Houghton Co.], Keweenaw Peninisula, Michigan, and named for United States geologist Raphael Pumpelly.