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The chemical formula of mineral Scheelite is indicated by CaWO4 or Calcium Tungstate. Scheelite is actually a Sulfate mineral. It is considered as an important source of tungsten. It is also rarely cut as gemstones and is also used as mineral specimen. Scheelite is usually found showing nice and interesting microscope appearance when viewed with the aid of petrographic polarizing microscope used in the field of optical mineralogy. As mentioned, Scheelite is an important ore of tungsten, a strategically important metal. Scheelite was named after K.W. Scheele, the discoverer of tungsten. Scheelite is especially abundant in US and it provides the United States with most of its supply. Scheelite is also popular among mineral collectors because of its fascinating appearance when viewed with the aid of polarized microscopes used in optical mineralogy. Scheelite is found forming perfect tetragonal dipyramidal crystals that look very much like octahedrons. Scheelite is isostructural with Powellite and both forms similar crystals. Scheelite fluoresces a bright blue color under short wave ultraviolet light. Massive Scheelite has often been mistaken for massive quartz.

             Scheelite is most commonly found showing white, orange, yellow or greenish gray to brown which can be seen more fascinating and more interesting when viewed with the aid of petrographic polarizing light microscopes. Scheelite is also showing adamantine to greasy luster when viewed in reflected light of polarized microscope used in the field of optical mineralogy. Most crystals of mineral Scheelite are found transparent to translucent in appearance. Scheelite is known to crystallize in the tetragonal system of crystal formation. In optical mineralogy, this tetragonal system comprises crystals having three axes, which are all in a position perpendicular to one another. Two axes are usually found having the same or equal length. The crystal habits of the mineral as described in the field of optical mineralogy usually include pseudo-octahedral crystals that are actually tetragonal dipyramids. Scheelite can be also found massive and granular in form.             Scheelite is usually found showing indistinct dipyramidal cleavage in two directions and good in another which can be seen more clearly exhibited when viewed with the aid of petrographic polarizing microscopes for mineralogists. Scheelite is also found showing conchoidal fracture when viewed with the aid of petrographic polarizing microscopes. The hardness measure of the mineral Scheelite when it is evaluated using the Mohs scale method is usually 4.58 to 5. Scheelite is most commonly found leaving a white streak when specimen sample is rubbed on a white porcelain streak plate. The specific gravity measure of the mineral is approximately 5.9 to 6.1 grams per cubic centimeters, which is very heavy for translucent minerals. Scheelite fluouresces blue under short wave ultraviolet light and yellow with molybdenum traces. Scheelite is most commonly associated with other interesting minerals including garnets, quartz, topaz, epidote, gold, silver and many more. The best field indicators of mineral Scheelite usually include color, crystal habit, luster, density and fluorescence. Scheelite notably occurs at several localities including Germany, Korea, Brazil, Mexico, England, Australia and some areas in USA.



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Thursday, August 13th, 2009 at 2:09 pm
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The Sulfates Mineral Class
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