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Click Here For Best Selection Of High Quality Polarizing Microscope

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The chemical formula of Perovskite is indicated by CaTiO3. This mineral is known to be pseudoisometric in structure. Sometimes monoclinic and sometimes orthorhombic in crystal system. Perovskite is an Oxide mineral. Perovskite is also an isotropic mineral. In optical mineralogy, isotropic minerals have no power to produce any illumination and they are singly refracting and consequently are quite dark when viewed between crossed nicols of petrographic polarizing microscope. They remain in that condition during a complete rotation of the polarized microscope stage. The index of refraction of mineral Perovskite is usually found ranging from 2.27 to 2.40. When mineral Perovskite is closely evaluated with the aid of polarizing microscope, it is commonly found exhibiting extreme relief in thin section.


            The chemical structure of Perovskite is consists of a cube with Ca at the center, with Ti at each corner, and O at the midpoint of each center edge. Most Perovskite minerals are close to the idealized composition. But then, other rare earth elements are commonly found in small amounts. The hardness measure of mineral Perovskite when it is evaluated using the Mohs scale method is usually found 5.5. The specific gravity measure of Perovskite usually ranges from 3.98 grams per cubic centimeters to 4.26 grams per cubic centimeters. It is usually found colored yellow, brown, or black in hand sample. When rubbed on a white porcelain streak plate, it is commonly found leaving a white or gray streak. Perovskite is also found showing adamantine to metallic luster when viewed in reflected light of polarizing microscopes used in optical mineralogy.


            Perovskite is commonly found colorless to shades of brown if evaluated in thin section or as fragments. It is rarely found gray or green when closely evaluated. Colored varieties may display weak pleochroism under petrographic polarizing microscope used in optical mineralogy. Perovskite usually forms tiny cubic or octahedral crystals that are more clearly exhibited when evaluated with the aid of polarized microscopes. When closely evaluated under petrographic polarizing microscope, Perovskite is commonly found exhibiting a poor cubic cleavage that is usually not seen due to small size grains but may be seen on large grains. Perovskite is commonly found displaying a complex lamellar twinning on one direction that can be seen clearly visible only in birefringent varieties.


            Perovskite is known to have biaxial positive figure although it appears essentially isotropic. Its optical angle is variable up to 90 degrees. The birefringence of mineral Perovskite is very low ranging from 0.000 to 0.002. It actually yields dark first-order gray colors in thin section. The interference color of Perovskite is usually noticed because of variation due to twinning. Small grains of Perovskite appear isotropic when viewed under polarizing microscopes used in optical mineralogy. But because mineral Perovskite is usually found in small grain size and with its very low birefringence, the interference figures are usually not obtainable.


            Perovskite may alter to leucoxene, a fine-grained white or gray aggregate consisting of Ti-bearing minerals such as rutile, brookite, and anatase. It can be also an alteration product after titanite and is commonly a constituent of leucoxene. Perovskite can be easily distinguished from other minerals due to its extreme relief, habit, lamellar twinning, and possible weak birefringence. Mineral Perovskite is usually found as tiny crystals in silica-deficient igneous rocks such as ijolites, peridotites, pyroxenites, syenites, and Leucite-bearing volcanic rocks. It can be also found in metamorphosed carbonate rocks and carbonatites.

Wednesday, May 28th, 2008 at 4:59 am
The Oxides and Hydroxides Mineral Class
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