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1 item @ $40.00  

Mineralpedia Details for Johnwalkite

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Johnwalkite

Johnwalkite

Named in honor of Richard Johnson (john) and Frank Walkup (walk), who were mineral preparers at the National Museum of Natural History in Washington D.C., USA. Johnwalkite is a rare mineral that can be found only here in the Black Hills of South Dakota in the Expectation pegmatite at the Champion mine, near Keystone. It is “a rare secondary mineral derived from the dissolution of triphyllite-lithiophilite and columbite-tantalite in a complex granite pegmatite.

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

Formula
K(Mn2+,Fe3+)2(Nb,Ta)O2(PO4)2ยท2(H2O,OH) 
Crystal System
Orthorhombic 
Crystal Habit
Prismatic, Radial, Aggregates 
Cleavage
Good, Good, None 
Luster
Vitreous (Glassy) 
Color
dark reddish brown, reddish brown 
Streak
greenish yellow 
Class
Orthorhombic - Pyramidal 
Fracture
Brittle 
Hardness
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Mindat
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Johnwalkite from Champion mine, Keystone, Pennington Co., South Dakota, United States

Johnwalkite
            from Champion mine, Keystone, Pennington Co., South Dakota, United States
Special Info
Co-Type

Dark red bladed crystals of Johnwalkite, around 1 cm.

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