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The chemical composition of mineral Bjarebyite is indicated by the formula (Ba,Sr)(Mn++,Fe++,Mg)2Al2(PO4)3(OH)3. Bjarebyite is usually found forming as a late-stage reaction product of triphylite and amblygonite in complex granite pegmatites. It is commonly found at Palermo #1 mine, near North Groton, Grafton County, New Hampshire, USA. This mineral was named for Alfred Gunnar Bjareby (1899-1967), Swedish-American student of New England pegmatite minerals. Bjarebyite 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.

            Mineral Bjarebyite is most commonly found showing perfect cleavage in two directions which can be found more clearly visible when viewed closely with the adi of petrographic polarizing microscope used in the field of optical mineralogy. This mineral is most commonly found colored emerald green in hand sample. The specific gravity measure of mineral Bjarebyite is commonly found 4.02 grams per cubic centimeters. Most crystals of mineral Bjarebyite are found transparent to translucent in appearance. The crystal habit of mineral Bjarebyite as described in the field of optical mineralogy commonly includes acicular forms occuring as needle-like crystals under polarizing microscopes. It can be also found prismatic where crystals are shaped like slender prisms. Sometimes crystals can be also striated with parallel lines on crystal surface or cleavage face. The hardness measure of mineral Bjarebyite when evaluated using the Mohs scale method is usually found 4. Bjarebyite is commonly found exhibiting subadamantine luster when viewed in reflected light of polarizing microscope. It is commonly found leaving a white streak when rubbed on white porcelain streak plate. Bjarebyite is also usually found showing biaxial positive figure when viewed closely between crossed nicols of polarizing microscopes. It commonly shows 0.0180 birefringence. Bjarebyite is also found pleochroic exhibiting colorless or pale brownish yellow color, brownish green or olive green to apple green. Bjarebyite is found to be a non-radioactive mineral after chemical evaluation.



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Saturday, January 15th, 2011 at 3:38 am
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Optical Mineralogy
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