10
GIA Polariscope
11
GIA Polariscope
Figure 3. A typical uniaxial figure (left) and a typical biaxial figure (right).
Figure 4. If optic colors are not visible, look for a dark shadow or
“brush.” Touch the optic figure sphere to the narrowest part of the brush to
observe the optic figure.
Detecting Pleochroism
The polariscope may be used to detect pleochroism in doubly refractive
colored stones.
To check for pleochroism:
1. Turn the analyzer to the uncrossed (light) position.
2. Place the stone on the sample plate or hold it between the polarizer and the
analyzer with your fingers.
3. Rotate the stone as you look through the analyzer noting any change in color as
the stone is rotated. Be sure to check in at least three different positions to be
sure you are not looking through an optic axis.
Use with Refractometer
The polariscope may be used to provide a white light source for the GIA
Refractometer as illustrated in figure 5.
(Refractometer not included)
Figure 5. Position the Refractometer in front of the white light port of
the polariscope.
