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Mineralpedia Details for Pecoraite

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Pecoraite

Pecoraite

Named after Dr. William Thomas Pecora, a former Director of the United States Geological Survey who studies nickel silicate deposits. Pecoraite is an uncommon mineral that forms as a result of the weathering of nickel-iron meteorite fragments in arid climates, along shear zones in ultramafic Archaean rocks, and in geodes. Pecoraite can be found in Australia, the United States, and Russia, among only a few others.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/pecoraite.pdf

Formula
Ni3Si2O5(OH)4 
Crystal System
Monoclinic 
Color
dark green 
Streak
light green 
Class
Monoclinic - Prismatic 
Hardness
2.5 
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Pecoraite from Otway Ni deposit, Nullagine, Western Australia, Australia

Pecoraite
            from Otway Ni deposit, Nullagine, Western Australia, Australia Dark green massive, dull grains.
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Pecoraite from Sterling mine, Antwerp, Jefferson Co., New York, United States

Pecoraite
            from Sterling mine, Antwerp, Jefferson Co., New York, United States

There is a bit of history behind this specimen, and we refer you to the MATRIX (Fall, 1995, v. 4) issue written by Steven C. Chamberlain. This is an excellent historical and mineralogical account of the first known Millerite locality in the USA. According to Chamberlain, George Robinson performed analytical work on the altered Millerite, which was thought to be Honessite (a likely guess). However, initial XRD work showed the alterations to be Jamborite. Further microprobe work revealed the alterations to be closer to Pecoraite. Robinson's work was not definitive nor all inclusive. This specimen has a beautiful spray of altered Millerite to 7mm tucked in vug of Hematite.

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