Under cross-polarized light, biotite exhibits extinction approximately parallel to cleavage lines, and can have characteristic bird's eye maple extinction, a mottled appearance caused by the distortion of the mineral's flexible lamellae during grinding of the thin section. See more Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula K(Mg,Fe)3AlSi3O10(F,OH)2. It is primarily a solid-solution series between the iron-endmember See more Members of the biotite group are found in a wide variety of igneous and metamorphic rocks. For instance, biotite occurs in the lava of Mount Vesuvius and in the Monzoni intrusive complex of the western Dolomites. Biotite in granite tends to be poorer in magnesium than … See more Like other mica minerals, biotite has a highly perfect basal cleavage, and consists of flexible sheets, or lamellae, which easily flake off. It has a See more Biotite is used extensively to constrain ages of rocks, by either potassium-argon dating or argon–argon dating. Because argon escapes readily from the biotite crystal structure at … See more
Bird
WebBird's eye extinction, or bird's eye maple, is a specific type of extinction exhibited by minerals of the mica group [1] under cross polarized light of the petrographic microscope. It gives the mineral a pebbly appearance as it passes into extinction. This is caused when the grinding tools used to create petrographic thin sections of precise ... WebIf they’re held up to the light, they’re obvious and almost colorless, however maximum have a mild brown, yellow, inexperienced, or rose-color tint. Name: From \Muscovy … chrome spinner hubcaps
Amphibolite - an overview ScienceDirect Topics
WebExtinction: Inclined (approximately 45 degrees). Parallel when viewed down (010); Sometimes displays hourglass extinction : Dispersion: r > v : Relief: High Positive : Twinning, Lamellae: Commonly displays simple and lamellar twinning on {100} and {001}; They may combine to form a herringbone pattern. Exsolution lamellae may be present. WebBiotite shows parallel extinction in cross polarized light, and has perfect cleavage in one direction. The biotite mineral shown here is exhibits bird's eye texture during … WebThe thin section captures the zone intruded by leucocratic veins during shearing. Garnet porphyroclasts are altered to biotite along their margins and in fractures. Quartz ribbons … chrome spindles for stairs