Learn · Gemstones and pearls
Birthstones around the world
The United States, Britain and Japan each keep their own official list, and India and Thailand have the much older tradition of nine gems. Pick a month to see every list side by side, with what each stone needs at the bench.
Pick a month; compare all the lists, or open one country's list.
Hue, tone and saturation
How the trade describes a coloured stone's colour: hue, tone and saturation
Where gems come from
A world map of where each gem is mined, today and historically
The 7 pearl value factors
GIA's seven pearl value factors, changed one at a time on one pearl
Gem treatments explained
Usual treatments gem by gem, the trade codes, care and disclosure rules
Cutting angles and light
Change a stone's cutting angles and follow the light: where it returns and where it leaks Preview