Pumpellyite Subgroup

Pumpellyite is named after Raphael Pumpelly, pioneer student of the detailed paragenesis of the copper minerals of the Keweenawan Peninsula, Michigan, where the mineral was discovered. Pumpellyite is Michigan's State Gemstone.

Pumpellyite forms translucent to opaque, blue-green, olive green to white fibrous to lamellar masses with glassy lustre.

Pumpellyite can be easily polished and cut into cabochons.
General Information
Varieties/Types:
Chemical Formula
Ca
 
2
(Mg,Fe,Mn,Al)
 
2
(SiO
 
4
)(Si
 
2
O
 
7
)(OH)
 
2
· H
 
2
O
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Photos of natural/un-cut material from mindat.org
Physical Properties of Pumpellyite Subgroup
Mohs Hardness5 to 6
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Specific Gravity3.20 to 3.30
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical Properties of Pumpellyite Subgroup
Refractive Index1.674 to 1.764
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical CharacterBiaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Birefringence0.014 to 0.016
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)Green, white
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Causes of ColourGreen (chlorastrolite), Fe2+-O-Fe3+ charge transfer coordination, plus Fe2+
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyOpaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Further Information
Mineral information:Pumpellyite Subgroup information at mindat.org
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