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The chemical formula of mineral Willemite is indicated by Zn2SiO4 or Zinc Silicate. Willemite is actually a Silicate mineral. It is considered as a minor ore of zinc and it is also used as mineral specimen. Willemite is somewhat rare zinc mineral but it was found with great abundance at Franklin New Jersey. Despite the fact that it was discovered at Franklin first, the mineral was named after one site in Belgium where the mineral formed small brown crystals that can be found more fascinating and more interesting when viewed with the aid of polarizing microscopes for mineralogists. It seems that the mineralogists at Franklin described the mineral but never named it. In the meantime, the mineral was named Willemite after William I of Belgium. Willemite is only one of the few Silicate minerals that have a trigonal symmetry. This symmetry is actually far more common among carbonates than among silicates. It was known in optical mineralogy that Willemite shares the same symmetry with the emerald green silicate dioptase and it is closely related to silicate mineral called Phenakite. Although massive Willemite is much more common, some crystals do show the rhombohedral terminations atop hexagonal prisms and this is actually a characteristic of its symmetry.

 

            Willemite is actually a fluorescent mineral. It is commonly found exhibiting a bright green fluorescent color under ultra violet light. Some Willemite specimens also shows phosphorescence. In the field of optical mineralogy, phosphorescence is the ability of a mineral to glow after the initial light is removed. The mineral has essentially stored the energy of the initial activating light and re-emits light on a delayed basis. Mineral Willemite is one of the best examples of a fluorescent mineral and it is actually a must have for any collector interested in this phenomenon. Willemite is usually found colorless or white but it can be also tinted yellow, blue, red, brown and often green in color that appear more fascinating and interesting when viewed with the aid of petrographic polarizing light microscopes used in the field of optical mineralogy. Willemite also exhibits vitreous to resinous luster when viewed in reflected light of petrographic polarizing light microscope used in optical mineralogy. Most crystals of mineral Willemite are found transparent to translucent in appearance. Willemite is also known to crystallize in the trigonal system of crystal formation.

 

            The crystal habits of mineral Willemite usually include the typical short prismatic crystals although some prismatic crystals can be rather long with sometimes very steep rhombohedral terminations. It is also found forming granular, lamellar and fibrous masses. Willemite is also found showing good basal cleavage in one direction. This can be found more clearly visible when specimen is evaluated more closely with the aid of polarized microscopes used in optical mineralogy. Willemite is also found showing conchoidal to uneven fracture when viewed with the aid of polarizing light microscopes for mineralogists. The hardness measure of mineral Willemite when it is evaluated using the Mohs scale method is usually found 5.5. Willemite is most commonly found leaving a white streak when specimen is rubbed on a white porcelain streak plate. The specific gravity measure of the mineral is approximately 3.9 to 4.2 grams per cubic centimeters, which is considered above average for non-metallic minerals. Willemite is usually found strongly fluorescent green and sometimes phosphorescent. Mineral Willemite is most commonly found associated with franklinite, calcite, zincite, Rhodonite, greenockite and other rare minerals. The best field indicators of mineral Willemite usually include associations, crystal habit, fluorescence, luster and cleavage. Willemite notably occurs in Belgium, Quebec in Canada, Namibia and Greenland aside from Franklin, New Jersey and Mammoth Mine in Arizona, USA.



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Friday, October 30th, 2009 at 2:57 pm
Category:
The Silicates Mineral Class
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