Pumpellyite is a group of closely related sorosilicate minerals:
pumpellyite-(Mg): Ca2MgAl2[Si2O6OH][SiO4](OH)2(OH)pumpellyite-(Fe2+): Ca2Fe2+Al2[Si2O6OH][SiO4](OH)2(OH)pumpellyite-(Fe3+): Ca2Fe3+Al2[Si2O6OH][SiO4](OH)2Opumpellyite-(Mn2+): Ca2Mn2+Al2[Si2O6OH][SiO4](OH)2(OH)pumpellyite-(Al): Ca2AlAl2[Si2O6OH][SiO4](OH)2OPumpellyite 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.
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