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Roger Weller, geology instructor                             

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Fluorescent Minerals
Steve Tyminski
Physical Geology
Fall 2007
                                                       Calcite
 

             Calcite, a carbonate mineral, is calcium carbonate and is one of the most widely distributed minerals on the Earth's surface. It is a common constituent of sedimentary rocks, limestone in particular.  It is also the primary mineral in metamorphic marble. Calcite occurs as a vein mineral in deposits from hot springs, and in caverns as stalactites and stalagmites.  Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence.  It is perhaps best known because of its power to produce strong double refraction of light, such that objects viewed through a clear piece of calcite appear doubled in all of their parts.  Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases.  When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures.[i]

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

 

         

          This example of willemite / calcite / hydrozincite is from the State of Texas Mine in the Huachuca Mountains of Cochise County, AZ.  Specimens are from the private collection of Roy Parsons.
 

7a

Willemite, Calcite, Hydrozincite, normal light
Willemite is white / Calcite dark gray, Hydrozincite dark

 

7b

 Willemite, Calcite, Hydrozincite, under ultraviolet light
Willemite is green / Calcite is red, Hydrozincite is blue

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