Gemology Fast Track / Unit 20 of 24 · Man-made & treated · 60 min
Treatments and disclosure
Goal: Know which treatments to expect per gem, how they're detected and what must be disclosed.
TreatmentTypical gemsDetection cluesStability
HeatCorundum, tanzanite, aquamarine, zircon, citrine, tourmalineAltered silk, discoid fractures (corundum); often undetectableStable
Oil / resin fillingEmerald, some rubyFlash effect, flattened bubbles, residuesCan dry/leak
Lead-glass fillingLow-grade ruby, sapphireFlash effect, bubbles, glassy surface areasFragile
Lattice diffusion (Be, Ti, Cr)Corundum, topaz, andesineColour rims, immersion; lab LA-ICP-MSSurface layer
IrradiationTopaz, diamond, tourmaline, quartz, beryl, pearlsOften undetectable; some fadeVaries
DyeChalcedony, jade, turquoise, quartzite, pearls, coral, lapisColour concentrated in cracks/grain boundaries; acetone swabCan fade/rub off
Bleach + polymerJadeite (Type B)Etched surface, FTIRDegrades
Stabilisation (resin)Turquoise, opal, amber, malachiteHot point smell, FTIR, low SGStable
CoatingTopaz, quartz, tanzanite, diamondWear at facet edges, iridescence, scratchesWears
Laser drillingDiamondDrill channel from surface to inclusionStable
HPHTDiamondLab onlyStable
Disclosure codes you'll see on reports
N — not enhancedE — enhanced (generic)H — heatedF — filledO — oiledR — irradiatedD — dyedU — diffusedW — waxed / colourless oil (porous gems)B — bleachedC — coatedI — impregnated (e.g. polymer)L — laser drilled
These follow the AGTA gemstone information codes; always read the report's own legend. The legal duty to disclose treatments applies under FTC guides (USA) and CIBJO rules internationally.
Assume treated unless proven otherwise
Ruby & sapphire
Heat
Emerald
Oil/resin
Tanzanite
Heat
Blue topaz
Irradiation
Turquoise
Stabilised
Black onyx, coloured agate
Dyed
Citrine
Heated amethyst
Red andesine
Cu-diffused
Practical
For each gem you own, write its most likely treatment from the 'assume' list and what test (yours or lab) would confirm it.
Unit quiz
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