Estimate a gem's value

How much is my stone worth?

This is the question that comes up most often, especially from those who inherit a piece of jewellery or a collection. Our calculator gives you an indicative price range from three simple inputs: the type of gem, its weight in carats, and the quality you perceive. It covers fourteen stones, from everyday amethyst to diamond, taking in sapphire, ruby, emerald, tanzanite, opal and tourmaline.

Why a range, and not a price

Because an exact price is impossible without examining the stone. The gem market is governed by factors that only physical examination can establish: colour (one shade can multiply value tenfold — the “pigeon's blood” red of a Burmese ruby has nothing in common with a pinkish ruby), clarity (inclusions visible to the naked eye send the price tumbling, with exceptions such as the emerald's “garden”), the cut and how well it is executed, geographic origin (a Kashmir sapphire is worth several times an equivalent stone from elsewhere), and above all the treatments it has undergone: heating, oiling, diffusion, glass filling.

Add to that certification: a stone accompanied by a report from a recognised laboratory sells for markedly more than the same stone without paperwork.

The weight rule: mind the trap

Price per carat is not linear. A 2-carat stone is not worth twice a 1-carat stone: it is often worth three to five times more, because large stones of fine quality are exponentially rarer. This is especially true of diamonds, where crossing the psychological thresholds (0.50 ct, 1 ct, 2 ct) triggers abrupt jumps in price.

Our tool therefore gives you an order of magnitude — useful for knowing whether you are being offered £50 or £5,000, not for haggling to the penny. To refine it, discuss it with our Lapidem Assistant, which knows the valuation factors; and for a firm valuation, consult a qualified gemmologist.