Roger Weller, geology instructor
Sphalerite is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. Miners have also been known to refer to sphalerite as zinc blende, mock lead, false galena and black-jack.
The mineral crystallizes in the cubic crystal system. The structure is closely related to the structure of diamond.
Its color is usually yellow, brown, or gray to gray-black, and it may be shiny or dull. Its luster is resinous. Some specimens are also fluorescent in ultraviolet light. Gemmy, pale specimens from Franklin, New Jersey are highly fluorescent orange and/or blue under longwave ultraviolet light and are known as cleiophane, an almost pure ZnS variety.[i]
This example of willemite / sphalerite is from the Nellie James Mine in the Huachuca Mountains of Cochise County, AZ. Specimen is from the private collection of Roy Parsons.
and Sphalerite, normal light
Willemite and Sphalerite are dark gray
and Sphalerite, under short wave ultraviolet light
Willemite is green, Sphalerite is orange
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