The lexicon
Gem trade glossary
The vocabulary of the coloured stone trade, defined the way labs and dealers actually use it. Every term links back to the catalogue it describes.
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- CabochonA stone polished into a smooth dome without facets.
- CaratThe trade's unit of weight, one fifth of a gram, divided into one hundred points.
- Certificate mismatchAny disagreement between a stone and the report accompanying it: weight, measurements or inclusions that do not correspond.
- Colour zoningUneven distribution of colour within a stone: straight bands, patches or sectors following the crystal's growth, common in sapphire.
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- PadparadschaA sapphire showing a delicate blend of pink and orange, named after the lotus blossom and historically associated with Sri Lanka.
- Pigeon's bloodA trade term for the most saturated pure red in ruby, historically tied to fine Mogok material whose strong fluorescence makes the colour appear lit from within.
- PleochroismThe property of showing different colours when viewed along different crystal directions.
- ProvenanceThe documented history of a stone: where it has been, who has owned it, which reports and invoices have travelled with it.
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