EOSC 118 Study Guide - Quiz Guide: Hexagonal Crystal Family, Cubic Crystal System, Crystal System
16 Apr 2014
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The average on the quiz was ~16. 1, and the following questions were some of the most commonly mis-answered. Please use these to help refine your learning, and please post any other questions you might have here! Remember also that we only take the top 3 of 4 quizzes in calculating your final course grade. Q: total internal reflection contributes to the brilliance of a gemstone by: A: returning light that enters through the crown and table of a gemstone back to our eyes. A: more than one refractive index along the crystallographic directions. The crystal system of a mineral will define whether it is anisotropic or isotropic. An anisotropic mineral can have either 2 or 3 distinct refractive indices, but they don"t necessarily need to be very different. The monoclinic, orthorhombic and triclinic systems have 3 refractive indices. The tetragonal and hexagonal systems have 2 refractive indices. Examples of anisotropic minerals include quartz, corundum, beryl, tanzanite, etc
