GIA Analyzing Gem Refractometer (c. 1949)

The GIA Analyzing Gem Refractometer was one of the first commercially available gem refractometers to incorporate built-in polarization (at 0° & 90°) and diffused-illumination control through a mechanical filter wheel. Documented in Gems & Gemology (Spring 1949), this arrangement allowed the operator to modulate polarization, contrast, and illumination directly within the refractometer—significantly improving shadow-edge visibility and analytical flexibility, all within one of the most compact refractometer designs of its era.

Built around a precision-ground truncated hemicylinder prism, the instrument was designed to provide stable and accurate critical-angle observations; at the same time, this refractometer maintained to be one of the smallest Refractometers ever made.

This is a museum archives and no unit is available for sale at this moment.