- Pumpellyite
Pumpellyite is a sorosilicate mineral rather a group of closely related minerals or
solid solution series:
*pumpellyite-(Mg): Ca2MgAl2(SiO4)(Si2O7)(OH)2·(H2O)
*pumpellyite-(Fe2+): Ca2FeAl2(SiO4)(Si2O7)(OH)2·(H2O)
*pumpellyite-(Fe3+): Ca2(Fe,Mg)(Al,Fe)2(SiO4)(Si2O7)(OH)2·(H2O)
*pumpellyite-(Mn2+): Ca2(Mg,Mn)(Al,Mn,Fe}2(SiO4)(Si2O7)(OH)2·(H2O)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 aMohs hardness of 5.5 and aspecific gravity of 3.2. I 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
basalt ic andgabbro ic rocks in metamorphic terranes. It is an indicator mineral of the prehnite-pumpellyite metamorphic facies. It is associated withchlorite ,epidote ,quartz ,calcite andprehnite . It was first described in 1925 for occurrences in the Calumet mine, Houghton Co., Keweenaw Peninisula,Michigan and named for U. S. geologist,Raphael Pumpelly (1837-1923).References
* [http://www.mindat.org/min-3309.html Mindat with location data]
* [http://www.webmineral.com/data/Pumpellyite-(Mg).shtml Webmineral data]
* [http://www.minsocam.org/msa/collectors_corner/arc/mipumpellyite.htm American Mineralogist, 1925]
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