Already measured your stone's refractive index? Enter it below — add birefringence too, if you have it — and see which gemstone species match.
The single RI value (or the higher of two shadow edges) read off your refractometer.
The difference between the two shadow edges. Leave the box above unchecked if you only saw one edge (singly refractive).
This tool suggests likely candidates based on typical published RI & birefringence ranges — it isn't a substitute for full gemological testing (specific gravity, pleochroism, spectroscopy, inclusions) for identifying or valuing a specific stone.