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Roger Weller, geology instructor                             

wellerr@cochise.edu

Fluorescent Minerals
Steve Tyminski
Physical Geology
Fall 2007
                                                      Powellite
 

            Powellite is a calcium molybdate mineral.  Powellite crystallizes as transparent adamantine blue, greenish brown, yellow to grey typically anhedral forms.  It exhibits distinct cleavage and has a brittle to conchoidal fracture.  It has a Mohs hardness of 3.5 to 4.  Powellite was first described in 1891 in the Peacock Mine, Adams County, Idaho and named for American explorer and geologist, John Wesley Powell (1834-1902).[i]

 

          This example of willemite / calcite / powellite is from the Nellie James Mine in the Huachuca Mountains of Cochise County, AZ.  Specimen is from the private collection of Roy Parsons.

 

1a

 Willemite, normal light
Willemite is gray, Calcite is white, Powellite is white

1b

 Willemite, ultraviolet light
Willemite is green, Calcite is red, Powellite is cream-white
 

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[i]  http://en.wikipedia.org/wiki/Powellite