Vote for your favorite mineral in #MinCup26! - Sphalerite vs. Anorthite
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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Forsterite from
Cotopaxi Mine (Cotopaxi lode; Gumaer Mine; Fannie lode; Fannie Mill), Mine Gulch, Cotopaxi, Cotopaxi Mining District, Fremont County, Colorado, USA


Locality type:Mine
Classification
Species:Forsterite
Formula:Mg2(SiO4)
Confirmation
Validity:Believed Valid
Data
Mineral Data:Click here to view Forsterite data
Locality Data:Click here to view Cotopaxi Mine (Cotopaxi lode; Gumaer Mine; Fannie lode; Fannie Mill), Mine Gulch, Cotopaxi, Cotopaxi Mining District, Fremont County, Colorado, USA
Data Identifiers
Mindat Occurrence Record ID:388201
Long-form Identifier:1:3:388201:6
GUID (UUID V4):0
Nearest other occurrences of Forsterite
38.6km (24.0 miles) ⓘSouth Park Basalt (2), South Park, Park County, Colorado, USA
42.4km (26.3 miles) ⓘBetty Mine (Lone Chimney Mine; Betty Lowe), Guffey Mining District, Park County, Colorado, USA
61.4km (38.2 miles) ⓘPortland Mine (Portland No. 1), Cripple Creek, Cripple Creek Mining District, Teller County, Colorado, USA
68.2km (42.4 miles) ⓘMarion Mine, Custer County, Colorado, USA
76.0km (47.2 miles) ⓘBadger Mountain, Guffey Mining District, Park County, Colorado, USA
References
Am Min 50:1179-1212
Eckel, Edwin Butt; Cobban, Robert R.; Mosburg, Shirley K.; Foord, Eugene E. (1997) Minerals of Colorado. Fulcrum Publishing.
Spry, Paul G.; McFadden, Scott; Teale, Graham S.; Alers, Brian; Shallow, John M.; Glenn, Justin M. (2022) Nodular sillimanite rocks as field indicators to metamorphosed massive sulfide deposits. Ore Geology Reviews, 141. 104632 doi:10.1016/j.oregeorev.2021.104632
 
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