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Both zinc ore Sphalerite and calcium plagioclase feldspar Anorthite have perfect cleavage that will split cleanly if you hit them with a hammer, but only one can claim a larger split of your votes!
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Stilpnomelane from
Pacheco Pass, Merced County, California, USA


Locality type:Pass
Classification
Species:Stilpnomelane
Formula:K4Fe482+[Si64Al8]O164(OH)52 · nH2O
Comments:Occurs in Franciscan Formation rocks.
Confirmation
Validity:Believed Valid
Associated Minerals:
Associates:Aragonite
Data
Mineral Data:Click here to view Stilpnomelane data
Locality Data:Click here to view Pacheco Pass, Merced County, California, USA
Data Identifiers
Mindat Occurrence Record ID:644255
Long-form Identifier:1:3:644255:2
GUID (UUID V4):0
Nearest other occurrences of Stilpnomelane
50.5km (31.4 miles) ⓘUnnamed Lawsonite-Glaucophane occurrence [1], Glaucophane Ridge, San Benito County, California, USA
52.1km (32.4 miles) ⓘPanoche Pass, San Benito County, California, USA
56.8km (35.3 miles) ⓘNew Almaden Mining District, Santa Clara County, California, USA
61.7km (38.4 miles) ⓘHillsdale Mine (Chaboya-Hillsdale Mine; San Juan Bautista Mine; San Juan Mine; San Juan Quicksilver Mine; Sheboya Mine; Chapman Mine; Oak Hill Mine), Oak Hill, San Jose, Santa Clara County, California, USA
90.4km (56.2 miles) ⓘVictor claim (Victor Mine), Picacho Peak, San Benito County, California, USA
References
McKee, Bates (1962), Widespread distribution of aragonite in the Pacheco Pass area, California (abstract): Geological Society of America Special Paper 68: 384
Pemberton, H. Earl (1983) Minerals of California. Van Nostrand Reinhold Company Inc.
 
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