Describe what you see. The model adapts its treatment, origin and clarity logic to each species and returns an indicative trade range.
Gem Index estimates the indicative wholesale trade value of transparent coloured gemstones — from sapphire, ruby and emerald to spinel, Paraíba tourmaline, tsavorite, alexandrite and tanzanite. Enter what you see — species, weight, colour, clarity, cut, treatment and origin — and the engine returns a per-carat price range and a total trade estimate across more than 78 varieties.
Each species carries a market-seeded base price per carat. That base is multiplied by colour (tone and saturation), clarity and transparency, colour zoning, cut and finish, any optical phenomenon, treatment, origin and size to reach an indicative wholesale range. The model adapts its logic to the gem: heated versus unheated corundum, oiling grades in emerald, copper-bearing Paraíba, and origin premiums such as Kashmir sapphire or Burmese ruby.
Across 15 families and 78+ varieties: Blue, Pink, Yellow, Teal, White and Padparadscha Sapphire, Ruby and Star Ruby, Emerald, Aquamarine, Morganite and Red Beryl, Pink and Grey Spinel, Paraíba, Rubellite, Chrome and Indicolite Tourmaline, Tsavorite, Demantoid, Spessartite and Rhodolite Garnet, Alexandrite, Tanzanite, Zircon, Peridot, Topaz, Amethyst, Citrine, Moonstone, Opal, Jade and rare collector stones.
In-depth, per-gem pricing guides: Sapphire price, Ruby price, Emerald price, Spinel price, Paraíba tourmaline price, Tanzanite price, Alexandrite price and Tsavorite garnet price.
It uses a multiplicative model: a market-seeded base price per carat for each species, adjusted by colour (tone and saturation), clarity, transparency, cut and finish, treatment, origin, certification and size to produce an indicative wholesale trade range.
More than 78 varieties across 15 families, including blue and padparadscha sapphire, ruby, emerald, pink and grey spinel, Paraíba tourmaline, tsavorite and demantoid garnet, alexandrite, tanzanite, aquamarine, zircon and peridot.
Yes. Gem Index is a free, browser-based coloured gemstone price calculator that returns an indicative per-carat trade range and a downloadable PDF estimate.
The figures are indicative trade estimates — not a formal appraisal or laboratory certificate. They are calibrated for transparent faceted coloured stones; species, treatment and origin should be confirmed by an accredited gem laboratory before sale.
Yes. The model adapts treatment logic per species (such as heated versus unheated corundum, or oiling in emerald), applies origin premiums (such as Kashmir or Burma), and factors clarity, transparency, colour zoning and cut quality.
Yes. Gem Index generates a downloadable A4 PDF estimate summarising the stone's attributes, the valuation factors and the resulting per-carat and total trade range.