The chemical formula of the mineral Aeschynite is indicated by (Y,Ca,Fe,Th)(Ti,Nb)2(O,OH)6 or Yttrium Calcium Iron Thorium Titanium Niobium Oxide Hydroxide. Aeschynite belongs to the Oxides and Hydroxides mineral class. Aeschynite is synonymous to priote and blomstrandine. Aeschynite is also a member of the group called Rare Earth Oxides. Those elements not used by other minerals in their composition gathered together under known conditions to form the rare earth oxides. Aeschynite mineral is known to crystallize in the orthorhombic system of crystal formation. In optical mineralogy, this orthorhombic crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths.
There are several minerals using Aeschynite in their names but they are actually distinct minerals with different compositions respectively. With regards to their mineral names, the prefixes and suffixes are the indicators of which rare earth metal is predominant in the mineral. Illustration follows: The Yttrium rich Aeschynite has the name Aeschynite – (Y).The Cerium rich Aeschynite has the name Aeschynite – (Ce).The Neodymium rich Aeschynite has the name Aeschynite – (Nd).The rich Niobium/Cerium Aeschynite has the name Niobo-Aeschynite-(Ce).
The Tantalum/Yttrium rich Aeschynite has the name Tantalaeschynite – (Y).
The kind of Aeschynite mineral being discussed here is the Aeschynite-(Y). The name origin of the mineral Aeschynite is the Greek word for shame. This is relative to the inability of the chemist to separate some constituents of the mineral at the time it was discovered. Another point of consideration is its chemical composition. Several color varieties are beautifully exhibited by mineral Aeschynite when it is closely viewed under a petrographic polarizing microscope used in optical mineralogy. Aeschynite usually displays pleochroic colors of black to dark brown when viewed in plane-polarized light of polarizing microscopes for mineralogists. Smaller crystal however, shows yellowish brown color when examined under polarized light microscopes for geologists.
Crystal appearances of mineral Aeschynite when it is viewed under petrographic polarizing microscope used in optical mineralogy are opaque if in massive formation and translucent if in small crystal formation. There can also be an inclusion of tabular to prismatic crystals, which can be seen when viewed under polarizing microscopes for mineralogists. Sometimes crystals tend to appear equant, while others appear to be domal and well formed when evaluated with the aid of polarized light microscopes for geologists.
Mineral Aeschynite usually exhibits vitreous to adamantine luster when viewed in reflected light of a petrographic polarizing microscope used in optical mineralogy. Sometimes if found in massive form, it shows pitchy luster under polarized microscope. Mineral Aeschynite has no cleavage planes visible even when it is closely evaluated under several adjustments on the aperture diaphragm of petrographic polarizing microscope for mineralogists. However, when the mineral is examined under several adjustments on the stage and aperture diaphragm of polarizing microscopes used in optical mineralogy, conchoidal fracture is highly visible. The hardness measure of mineral Aeschynite when it is evaluated using the Mohs scale method is usually found ranging from 5 to 6 giving an average of 5.5. The specific gravity measure of Aeschynite is approximately 4.9 grams per cubic centimeters to 5.1 grams per cubic centimeters, which is considered heavy for non-metallic minerals even at 5 grams per cubic centimeters average. Streak is reddish brown and sometimes reddish yellow in appearance when Aeschynite is rubbed on a white porcelain streak plate.
This Aeschynite is considered optically isotropic or singly refractive mineral. In optical mineralogy, isotropic means the mineral section has no power to produce any illumination and they consequently appear dark when viewed in different angles and stage rotations of geological polarizing microscope. They exhibit very weak pleochroism when viewed in plane-polarized light of petrographic polarizing microscope. Aeschynite is commonly found as constituent of some slow cooling igneous intrusive rocks like some rare earth rich granite pegmatites. They often appear splendidly embedded in pegmatic host rocks. They are commonly found in granular and massive forms.
