Editor’s Note
The rise of synthetic diamonds is reshaping the jewelry industry, challenging traditional value perceptions and impacting natural diamond pricing. This article explores the profound market shifts signaled by a simple slogan at a Hong Kong trade fair.
Last September, at the annual Jewellery & Gem World trade show in Hong Kong, this slogan blared by a manufacturer inadvertently provided a striking X-ray of an industry in full transformation. The main challenge is this: synthetic diamonds are everywhere. They are featured in nearly half of the engagement rings sold in the United States. Yet their perceived value is now close to zero. Even more serious, they are causing a halo effect, dragging down the prices of natural diamonds. A one-carat, colorless, well-cut, high-quality natural diamond sold for around $8,000 in 2007. Today, the average price for an equivalent stone is closer to $5,000.
Colored diamonds attract a clientele seeking exclusivity. Their rarity has increased with the depletion of certain mines, like Argyle in Australia. In the photo: the “Rainbow” collection of 300 unmounted colored diamonds, patiently assembled over a lifetime by Eddy Elzas, was auctioned by Christie’s in Geneva in November 2025.
But comparison is not always valid. The entrepreneur could also have cited the massive arrival of cultured pearls, which coincided with the drastic fall in the value—though immense—of natural pearls in the early 1930s (Pierre Cartier had exchanged a necklace of natural pearls for a building on Fifth Avenue), or the predicted death of the mechanical watch industry in the late 1970s during the quartz craze. In these two examples, it is interesting to note that the value of fine pearls has risen (though not reaching its peak level achieved during the Belle Époque) since the early 1990s after several decades of stagnation. The mechanical watch, for its part, remains the engine of luxury watchmaking. So, no need for catastrophism. Certainly, stocks of stones are accumulating and prices are under pressure, but market agility could restore the luster to a material laden with geological and cultural memory.
The price of blue diamonds, above a certain weight, hovers around 2 million euros per carat. In the photo, the “De Beers Blue Cullinan,” originating from a 39-carat rough extracted by Petra Diamonds from the Cullinan mine in 2021 before being sold to De Beers and Diacore. Auctioned by Sotheby’s in Hong Kong in 2022, the cut diamond, with a final weight of 15.10 carats, was sold for $57.47 million. That’s $3.8 million per carat.
says diamond dealer and gemologist Jonathan Ghenassia. The expert prophesies:
Does this mean that owners of a rare natural stone, of substantial weight (ideally over 5 carats) and adorned with a color, are assured of making a good investment?
Not quite. Auctioned last November at Christie’s in Geneva, the “Mellon Blue” diamond, a vivid blue pear-shaped specimen of 9.51 carats that belonged to American heiress Rachel Lambert Mellon, was sold for $25 million. That’s $2.7 million per carat. A considerable sum. The most expensive lot of the year. However, this same stone had already appeared in 2014 in New York. Billionaire Joseph Lau had bought it for $32 million. A decline in enthusiasm among collectors or circumstantial caution? Nevertheless, the announcement on January 13th by mining company Petra Diamonds of the discovery of an exceptional stone—a 41.82-carat blue diamond—could change the game.
The Cullinan mine in South Africa has, throughout its history, supplied some legendary jewels to the British crown as well as several highly sought-after Type IIb blue diamonds that have shattered records at public auctions.