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The chemical formula of mineral Polybasite is indicated by (Ag, Cu)16Sb2S11 or Silver Copper Antimony Sulfide. Polybasite is actually a Sulfide mineral. Mineral Polybasite is also considered as an ore of silver. It is also most commonly used as mineral specimen and it is most often found showing nice and interesting microscope image when viewed under polarizing light microscope used in the field of optical mineralogy. Polybasite is actually a somewhat uncommon silver bearing mineral that exhibits wonderful appearance when viewed under polarized microscope for mineralogists. Despite the fact that it is not a well-known ore of silver, it is regarded as a locally important ore in some mines. Polybasite is usually found forming very interesting crystals that have a pseudohexagonal outline with rhombohedral striations. Although its symmetry is monoclinic, the nearly hexagonal crystals and striations suggest that it has a higher temperature phase that is hexagonal or trigonal in form.

 

            Mineral Polybasite is known to be forming a solid solution series with the mineral pearceite. In optical mineralogy, it has been known that the two minerals can substitute the antimony for the arsenic within their structures. Polybasite is known to be quite difficult to distinguish from mineral hematite and stephanite. Hematite is actually an oxide mineral while stephanite is another silver antimony sulfide mineral. Hematite usually forms metallic steel gray platy crystals but has a blood red streak and is considerably harder. Stephanite on the other hand lacks the rhombic striations on the pinacoidal faces, the red flashes and the good cleavage of Polybasite.

             Mineral Polybasite is most commonly found showing iron black to a cherry red color in thin section with slight flashes of red possibly seen on some crystal surfaces when specimen is closely evaluated using the polarizing microscope used in optical mineralogy. Polybasite is also most commonly found showing metallic luster when viewed under petrographic polarizing light microscope used inn optical mineralogy. Most crystals of mineral Polybasite are found opaque to translucent in appearance especially in thin sections or crystal edges. Mineral Polybasite is known to crystallize in the monoclinic system of crystal formation. In optical mineralogy, the monoclinic system of crystal formation comprises crystals having three axes of unequal lengths. Two of which are usually found in a position that is oblique or not perpendicular to one another. However, both of which are commonly found perpendicular to the third axis.  The crystal habit of mineral Polybasite as described in optical mineralogy usually includes pseudohexagonal plates or tablets that can be more interesting when viewed under polarized microscopes for mineralogists. Polybasite is also usually found massive in form. Polybasite is also usually found showing perfect basal cleavage in only one direction when specimen is viewed closely under polarizing microscope used in optical mineralogy. Polybasite is also most commonly found showing uneven fracture when evaluated under polarized microscopes. The hardness measure of mineral Polybasite when it is evaluated using the Mohs scale method is usually ranging from 2 to 3. The specific gravity measure of the mineral is approximately 6.1 grams per cubic centimeters to 6.3 grams per cubic centimeters, which is heavy even for metallic minerals. Mineral Polybasite is also most commonly found leaving a black to reddish black streak when specimen is rubbed on a white porcelain streak plate. Polybasite mineral crystals are partially malleable. Its crystals are sometimes showing rhombic striation pattern and dark coating can often form after prolonged exposure to light. This can actually be removed by ultrasonic treatment. The best field indicators of mineral Polybasite usually include density, crystal habit, and association with other silver sulfosalts as well as softness, color and cleavage. Polybasite is also usually found associated with other interesting minerals including quartz, stephanite, galena, acanthite, silver, proustite, Pyrargyrite, tetrahedrite and other silver sulfide minerals. Polybasite notably occurs at several localities including Mexico, Germany, Chile, Sardinia, Bolivia, Australia and some areas in USA.



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Monday, June 29th, 2009 at 2:33 pm
Category:
The Sulfides Mineral Class
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