General Information:
Chemical Formula:
Mn++6V+++++2Si2(O,OH)14
IMA Status:
Approved IMA
Locality:
Pennsylvania mine, SW side of San Antonio Valley, 4 miles ENE of Mount Halilton, Santa Clara Co. California.
Name Origin:
Named after the Miocene age Franciscan Formation.
Physical Properties:
Color:
red.
Density:
4.1
Diaphaniety:
Transparent to Translucent
Hardness:
4 - Fluorite
Luster:
Vitreous (Glassy)
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