光性礦物實習期末考 June 8, 1999
1） What is Becke line? How to use it to determine refractive index of a
mineral under microscope?
2） Explain what is: (a) open nicol; (b) close nicol; (c) parallel nicol.
3） Given a retardation △＝700mm for a mineral thin section, what is its
interference color? And what is its interference color under parallel
nicol condition?
4） How to distinguish first order white from high order white?
5） How to determine elongation sign of a mineral under microscope?
6） Describe the extinction angle of hornblende.
Is that possible hornblende exhibit an extinct angle of 0o or 45o? Why?
7） How to determine the optical sign of a mineral?
8） Describe how to distinguish following minerals under microscope.
a) hornblende, biotite and augite.
b) calcite, quartz, feldspar.
9） Describe the following optical phenomenon under microscope.
a) saussuritization
b) perthite
c) zoning
10） Please pick out the minerals, which exhibit the optical characters of
changeable relief as rotating stage from the following list.
11） Please pick out the minerals, which exhibit the optical characters of
pleochroism from the following list.
12） Please pick out the minerals, which always exhibit parallel extinction
from following list.
13） Please pick out the minerals, which are transparent and isotropic under
microscope from following list.
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