What Is the Most Expensive Gemstone in the World?

The price of a precious stone per carat can range from a few hundred to several million euros depending on quality. Below are the four great gemstones ranked by their maximum value potential.

The ruby is, carat for carat, the precious stone most likely to reach record prices. Its exceptional value stems from a unique confluence of factors: absolute rarity, incomparable colour and a millennia-old history.

The world reference colour is "pigeon blood" — a vivid, slightly bluish red evoking the blood of a pigeon. This precise term, now certified by gemmological laboratories, designates rubies from Burma (Mogok) of irreproachable saturation and luminosity. Their natural fluorescence under sunlight further intensifies their brilliance, creating an inner glow that no other stone can replicate.

Fine untreated rubies of more than 3 carats are so rare that they are traded almost exclusively between private collectors and the great auction houses. In accessible jewellery, a beautiful ruby of 0.80 to 1.50 carats already offers extraordinary colour and presence for a unique ruby engagement ring.

The white diamond remains the most popular precious stone for engagement rings, yet its per-carat value is far from the highest among gemstones. A white D-IF diamond (colourless, inclusion-free) of 1 carat is worth between 8,000 and 15,000 € — whereas a ruby or Kashmir sapphire of the same weight can be worth ten to one hundred times more.

It is with its coloured varieties — known as "fancy diamonds" — that the diamond reclaims its place among the world's most expensive gemstones. Pink diamonds, sourced principally from the Argyle mine (Australia, closed in 2020), have become exceptionally rare. Blue diamonds, whose colour is caused by the presence of boron, rank among the most coveted stones in the world.

Among sapphires, origin is decisive in determining value. A fine-quality sapphire from Sri Lanka or Madagascar is worth between 3,000 and 20,000 € per carat. But a Kashmir sapphire — whose deposits were exhausted in the 1930s — can exceed 100,000 € per carat.

The colour of Kashmir is described as a velvety blue, or a "sleeping blue": an intense saturation with a subtle diffuse transparency that renders the stone luminous even in low light. This quality is the result of specific micro-inclusions that scatter light in a wholly unique way — impossible to replicate through treatment or synthesis.

Large untreated Ceylon (Sri Lanka) sapphires also represent a sound investment, with their highly prized cornflower blue hues sought after by bespoke jewellery houses.

The emerald holds a singular place in the world of gemstones. While fine-quality emeralds are accessible from €2,000 to €8,000 for an engagement ring, large untreated Colombian emeralds enter an altogether different scale of value.

The benchmark colour — "muzo green", named after the Colombian Muzo mine — is a warm, slightly bluish green with an inner luminosity that no treated emerald can match. A certificate attesting to the complete absence of treatment (no oil) can multiply the value of an emerald by three to five times compared with a treated stone of the same colour.

Beyond the classic 4Cs, several factors specifically determine the market value of a coloured precious stone. Here they are, in order of importance.

Precious stones of exceptional quality have historically weathered economic crises well. Unlike financial assets, a fine certified gemstone is tangible, portable and universally recognised. It represents a discreet store of value that some investors incorporate into their wealth portfolio.

Untreated Burmese rubies, Kashmir sapphires and untreated Colombian emeralds are the three categories that have performed best over the past twenty years. Their increasing rarity — the historic deposits being exhausted or on the verge of exhaustion — structurally underpins their long-term value.

At Bonnot Paris, we guide clients who wish to combine beauty with lasting heritage value in the selection of their bespoke jewel. Our direct sourcing in India, Sri Lanka and Thailand enables us to identify stones of strong potential well before they enter the European market.