A quiz about a mineral optic figure: just experimenting with the codeLast Updated: 22nd Mar 2020
By Frank K. Mazdab
After watching this short (30 sec) video of an optic figure, please answer the accompanying questions:
1. What is the optical nature of this mineral?
2. Based on the optical nature of this mineral, select all of the possible crystal systems that could be consistent with this figure?
3. Based on the figure, what is the optic sign of this mineral? Assume the microscope uses a standard accessory plate orientation, with the "slow" ray vibration direction of the accessory plate oriented NE-SW.
4. Assuming the entire diameter of the circular field of view represents a 2V° angle of 60°, approximately what 2V° angle is shown by the mineral in this figure?
5. Based on the figure, which answer best describes the observed dispersion of this mineral?
6. Based on your answers to the preceding questions, and using the mindat database to look up optical properties (check the links provided), which one of the following minerals is most likely represented by this optic figure?
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