Mineralpedia Details for 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
- 4
- WebMineral
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Johnwalkite from Champion mine, Keystone, Pennington Co., South Dakota, United States
- Special Info
- Co-Type
Dark red bladed crystals of Johnwalkite, around 1 cm.
Click thumbnail images for larger view.
