Gemstone specifications

Gemstone Specifications

Coloured gemstones have very different value drivers from diamonds — origin and treatment can swing value by an order of magnitude.

Type

Sapphire, Ruby, Emerald, Opal, Tanzanite, Tourmaline, Aquamarine, Topaz, Amethyst, Citrine, Garnet, Pearl, or Other.

Carat

Weight in carats. For multi-stone pieces, enter total carat weight here and the breakdown in Description.

Origin

Country of origin where known. For sapphires this is huge: Kashmir > Burma > Ceylon > Madagascar in typical retail-value terms.

We surface a Geographic Origin picker for sapphires, rubies and emeralds because the market premium is so significant.

Treatments

• None: untreated, no enhancement
• Heat: standard for most sapphires and rubies; well-disclosed and accepted
• Diffusion: surface or lattice; disclose explicitly, lowers value
• Oil / resin: standard for emeralds; grade as Minor / Moderate / Significant
• Beryllium: significant value impact for sapphires; must be disclosed

Lab certificate

GRS, Gübelin, SSEF and AGL are the leading coloured-gem labs. Enter the lab and report number for verifiable provenance.

Pearls (special case)

For pearls, instead of carat use the millimetre size and string length. Track the type (Akoya, South Sea, Tahitian, Freshwater) and lustre grade.