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Pumpellyite-(Mn2+)-Osumilite-Mg 1.65 ct.



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Pumpellyite-(Mn2+)-Osumilite-Mg 1.65 ct.

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Pumpellyite is a group of closely related sorosilicate minerals:

  • pumpellyite-(Mg): Ca2MgAl2[(OH)2|SiO4|Si2O7]·(H2O)

  • pumpellyite-(Fe2+): Ca2Fe2+Al2[(OH)2|SiO4|Si2O7]·(H2O)

  • pumpellyite-(Fe3+): Ca2(Fe3+,Mg,Fe2+)(Al,Fe3+)2[(OH,O)2|SiO4|Si2O7]·H2O

  • pumpellyite-(Mn2+): Ca2(Mn2+,Mg)(Al,Mn3+,Fe3+)2[(OH)2|SiO4|Si2O7]·(H2O)

  • pumpellyite-(Al): Ca2(Al,Fe2+,Mg)Al2[(OH,O)2|SiO4|Si2O7]·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 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 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).(from Wikipedia).

Here is associated with Osumilite-Mg in layer-like structure in metamorphic quartzite.

The Osumilite-Mg is a very rare hydrate potassium-sodium-iron-magnesium-aluminium silicate mineral. Osumilite is part of the milarite group (also known as the milarite-osumilite group) of cyclosilicates.The formula is (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30·H2O and hardness 5-6.

This material comes from Vassiliko, Katakalaii, Andros Island, Aegean Sea,Greece.

Size:8.7x6.1x4.2 mm.

Weight:1.65 ct.


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