Pumpellyite

Pumpellyite series

hardness5.5-6LusterVitreous, dullStreakWhiteDiaphaneityTranslucentSpecific gravity3.2References^[2] ^[3]

Pumpellyite is a group of closely related sorosilicate minerals:

pumpellyite-(Mg): Ca₂MgAl₂[Si₂O₆OH][SiO₄](OH)₂(OH)^[4]
pumpellyite-(Fe2+): Ca₂Fe²⁺Al₂[Si₂O₆OH][SiO₄](OH)₂(OH)^[5]
pumpellyite-(Fe3+): Ca₂Fe³⁺Al₂[Si₂O₆OH][SiO₄](OH)₂O^[6]
pumpellyite-(Mn2+): Ca₂Mn²⁺Al₂[Si₂O₆OH][SiO₄](OH)₂(OH)^[7]
pumpellyite-(Al): Ca₂AlAl₂[Si₂O₆OH][SiO₄](OH)₂O^[8]

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 n_α=1.674–1.748, n_β=1.675–1.754 and n_γ=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 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 Co., Keweenaw Peninisula, Michigan, and named for United States geologist Raphael Pumpelly (1837–1923).^[9]

References

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ Mineralienatlas
^ Chesterman, Charles W. (1978). The Audubon Society field guide to North American rocks and minerals. New York: Alfred A. Knopf. p. 567. ISBN 0394502698.
^ Mindat - Pumpellyite-(Mg)
^ Mindat - Pumpellyite-(Fe2+)
^ Mindat - Pumpellyite-(Fe3+)
^ Mindat - Pumpellyite-(Mn2+)
^ Mindat - Pumpellyite (Al)
^ Huber, N. King (1975). The Geologic Story of Isle Royale National Park, USGS Bulletin 1309. Washington: U.S. Government Printing Office. p. 58.