EARTHSC 1108 Lecture Notes - Lecture 4: Peridot, Orthorhombic Crystal System, Nondestructive Testing
1 Dec 2016
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Document Summary
Gem optical properties refraction and polarized light. Ratio between the speed of light in air to the speed of light in a stone. Ri of gems are between 1. 4 and 3. 2 (some have 2 ris ) Ri linked to critical angle by snell"s law: very clear curve. Ri is constant for each specific gem. Can be used to identify mounted stones. Gems with flat and/or well-polished surfaces work best for measuring refractive index. Ri for gems is always greater than 1. 4. Most gems have more than one refractive index (sr), these are known as doubly refractive (dr) gems. Measures critical angle, and does the math to ri: measures the refractive index by determining critical refraction angle critical angle refractometer . Iso-tropic: same-manner in greek, light behaves same in all directions in the crystal, cubic system. An-iso-tropic: not-same-manner in greek, light moves differently in different directions in the crystal, splits light wave into 2 perpendicular waves, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal.
