Gemmological microscopy examines the characteristic properties of stones, e.g. for quality controls (clarity, cut, carat)
Dichroscopes reveal whether transparent, coloured gemstones exhibit pleochroism, i.e. direction-dependent polychromatism.
In gemological spectroscopy, absorption spectra of coloured stones can be generated and analyzed with reference spectra.
Gemstone refractometers use the total reflection of polished stones to determine their refractive index. This determines the type of stone, characteristics and quality.