EARTHSC 1108 Lecture Notes - Lecture 6: Iridescence, Chrysoberyl, Incandescent Light Bulb
5 Apr 2016
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Document Summary
Color of a gem changes with change in orientation. A stone must be dr to display true pleochroism. Some gems can be trichroic (rare and valuable) Pleochroic gem rough normally is cut to maximize the beauty of color variation ex: tanzanite. Will normally be cut to maximize the attractive pleochroic colors. Oriented to minimize the effect of the greenish yellow hues. Proper orientation of the gem is most important! Strong light source is shined through the stone. The dichroscope is oriented to view light passing through the gem. Gem variety alexandrite exhibits a color change that varies with the source of light. Some materials glow (fluoresce) when exposed to uv radiation. As with color, electrons are excited to higher energy levels (1 to 2) Electrons fall back to a lower energy state, but not to the ground state (2 to 3) Fluorescence sometimes can be used to identify a gem.
