Gemology Fast Track / Unit 1 of 24 · Foundations · 60 min
How gems are identified
Goal: Know the vocabulary and the decision path every ID follows.
Species
Defined by chemistry + crystal structure. Corundum = Al₂O₃, trigonal.
Variety
Trade name inside a species, usually by colour or phenomenon. Corundum → ruby, sapphire.
Group
Related species sharing a structure. Garnet group = pyrope, almandine, spessartine, grossular, andradite, uvarovite.
Four questions for every stone
1 · What species?RI, SG, optic character, spectrum, inclusions
2 · Natural or man-made?Synthetic = same species made in a lab. Simulant = looks like it, different material.
3 · Treated?Heat, filling, diffusion, irradiation, dye, coating
4 · Quality?Colour, clarity, cut, carat (+ origin for high-end)
Material types you must separate
Natural
Formed in nature.
Synthetic / lab-grown
Same chemistry, structure and properties as the natural species.
Simulant / imitation
Different material: CZ for diamond, glass for anything.
Assembled
Doublets and triplets: two or more pieces glued or fused.
Which tests carry the weight
Colour is the weakest clue: almost every colour exists in a dozen species. Never ID by colour.
Value drivers (coloured stones)
Colour ≈ most of valueClarity (by type)Cut / brillianceSizeTreatment statusOrigin (top stones)Rarity / demand
Practical
Lay out every stone you own. Sort into piles by colour only. Write down your species guess for each. Keep the list; you'll re-sort it by measured RI/SG in Unit 9 and see how wrong colour sorting is.
Unit quiz
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