Conoscope

Polarizer accessories
It is used to observe the interferogram of heterogeneous gemstones and determine the axial and optical symbols.

The conoscope, is an accessory tool to the polariscope. It allows visualizing the optical axes of a birefringent and transparent mineral.

Method Of Application
First you observe your specmien under the polariscope. Find the interference colors of the optical axis C. Then put the conoscope in place, between the polarizing filters above the stone. Here you will discover the axes.
Note that at least one facet needs to be exactly perpendicular to the optical axis, oterhwise you will not see the axes. When observing a cobochon or a spere the axes are easier to find.