ERSC 2P21 Lecture Notes - Lecture 3: Birefringence, Iridescence, Pyrite
18 Dec 2018
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Document Summary
Physical properties: a macroscopic expression of a mineral"s internal make up. Diamond, c: hardness (h) = 10, network of carbon atoms. Graphite, c: hardness (h) = 2, sheets of carbon that are weakly held together. Crystal shape: the outward appearance of a mineral takes on a regular, geometric shape, the outward expression of the internal ordered atomic arrangement, galena, pbs. Perfect and distorted crystal shapes dodecahedron pyritohedron rhombohedron octahedron. Crystal form: external morphology of a crystal under ideal growth conditions, reflects the crystal system quite well. Crystal habit: typical (non-ideal) shape of a crystal or aggregate of crystals, can contrast with ideal crystal form, limitations due to space, time, impurities, etc. Quality of external planes: euhedral: completely bounded by crystal faces, euhedral almandine garnet, subhedral: partly bounded by crystal faces, anhedral: lacks crystal faces, may have rounded or irregular surfaces. Prismatic: elongated crystals that are thicker than needles, e. g. , apatite.
