Cochise College Student Papers in Geology
Geology Home Page physical geology historical geology planetary gems
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.
Willemite,
normal light
Willemite is gray, Calcite is white, Powellite is white
Willemite,
ultraviolet light
Willemite is green, Calcite is red, Powellite is cream-white