The chemical formula of mineral Aragonite is indicated by CaCO3. Aragonite is a Carbonate mineral. It is known to crystallize in the orthorhombic system. In optical mineralogy, the orthorhombic crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths. When viewed under polarizing microscopes used in optical mineralogy, Aragonite is commonly found exhibiting a biaxial negative figure. The indices of Aragonite are usually found ranging from 1. 530 to 1.685. The birefringence of the mineral is commonly found 0.155. The optic angle of the mineral is about 18 degree. When evaluated under petrographic polarizing light microscope, Aragonite is commonly found exhibiting a low negative to high positive relief, depending on orientation. However, Aragonite may show a marked change of relief with the stage rotation of the polarized microscope.

 

            Aragonite is commonly found having hardness measure ranging from 3.5 to 4 when evaluated using the Mohs scale method. The specific gravity measure of the mineral is usually found to be around 2.94 grams per cubic centimeters. Aragonite is commonly found white or colorless in hand sample. It may also be found gray, yellow, green, blue, violet, or rosebud. When rubbed on a white porcelain streak plate, Aragonite is commonly found leaving a white streak. When viewed in reflected light of polarizing microscope used in optical mineralogy, Aragonite is most commonly found exhibiting a vitreous luster. It also effervesces vigorously in cold dilute HCl.

 

            Aragonite is commonly found colorless if in thin section or even as fragments. Aragonite is usually found as radiating or columnar aggregates of grains elongate grains that are splendidly exhibited when viewed under polarized microscope. Aragonite crystals are typically twinned and usually produce cyclic twins with six segments that are very visible in basal sections of the mineral when viewed with the aid of the petrographic polarizing light microscope. Twinning may also be polysynthetic.

 

            When closely evaluated with the aid of the petrographic polarizing microscope, Aragonite is commonly found having single imperfect cleavage in one direction and a poor prismatic cleavage on one direction. But then, this cleavage may not be usually found. The extinction of Aragonite is usually found parallel to crystal elongation and to the trace of the cleavage in longitudinal sections. The fast ray of Aragonite is commonly found vibrating parallel to the length of columnar crystals and parallel to the cleavage traces in both basal and longitudinal sections.

 

            The indices of mineral Aragonite as noticed are vary relatively little. Because the birefringence of the mineral is extreme, it yields a creamy high-order white interference colors in both thin section and grain mount for most orientations. This is of course with the exception of those with vertical optic axis. When basal section of Aragonite is examined closely between crossed nicols of the polarizing light microscope, it is commonly found with acute bisectrix figures with isogyres that are relatively thin at the metalopes. This actually broadens toward the edge of the microscope field of view. The optic axis dispersion of the mineral is very weak. Aragonite may be replaced by dolomite or other minerals. It may also convert to its pseudomorph calcite. Aragonite is most commonly found in carbonate-bearing blueschist facies metamorphic rocks. It also precipitates directly from the sea. There are also reported occurrences of Aragonite at the oxidized zone of hydrothermal sulfide mineral deposits. Also at some iron-rich sediments.