Gemstone Reference Guide
Scientific optical properties, mineral classifications, and diagnostic features for major gemstone species.
Major Gemstone Categories & Properties
Key physical optical constants for essential precious and semi-precious gem species.
Ruby
Red gem variety of Corundum ($Al_2O_3$) colored by trace chromium ($Cr^{3+}$).
Sapphire
Non-red gem variety of Corundum (blue, yellow, pink, green) colored by iron ($Fe$) and titanium ($Ti$) intervalence charge transfer.
Emerald
Green gem variety of Beryl ($Be_3Al_2Si_6O_{18}$) colored by chromium and/or vanadium.
Topaz
Fluosilicate mineral ($Al_2SiO_4(F,OH)_2$) occurring in blue, imperial orange, pink, and colorless varieties.
Garnet
Isomorphous group of silicate minerals (Almandine, Pyrope, Spessartine, Grossular, Tsavorite).
Tourmaline
Complex borosilicate mineral displaying strong dichroism (Elbaite, Rubellite, Indicolite, Paraiba).
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