• HB Antwerp claims producers can increase revenues by up to 40% using its polished-value pricing model.

• The approach focuses on large, high-quality stones (+10.8 carats) at Botswana’s Karowe mine, raising doubts about its wider applicability.

• Weak demand and competition from lab-grown diamonds have cut De Beers’ Q1 2025 revenue by 44% and forced Lucara to slash its annual forecast.

Diamond companies are adjusting their sales strategies as global demand weakens. In Africa, De Beers has reduced supply and intensified promotion of natural stones.

Oded Mansori, co-founder of Belgian diamond trading firm HB Antwerp, said producers must rethink marketing methods to maximize revenue in a depressed market. He argued that companies can earn up to 40% more by pricing stones based on their final polished value rather than through auctions and long-term contract sales.

“For years, miners relied on tenders and auctions, systems that look efficient on paper but in practice resemble a casino,” Mansori said in comments relayed by Reuters on September 18. “Rough stones are pushed into opaque markets where value is anyone's guess. When global demand softens, as it has in cycles over the last decade, producers are left exposed. Workers pay the price, while shareholders watch assets decline.” 

HB Antwerp’s Model Under Scrutiny

HB Antwerp uses this polished-value model in partnership with Lucara Diamond, operator of the Karowe mine in Botswana. The approach ties producer revenues not to the estimated price of rough stones at auction but to their actual value after cutting and polishing, allowing miners to capture added value along the supply chain.

However, the system faces questions. Critics note its concentration on large or high-quality stones. At Karowe, HB Antwerp buys rough diamonds of more than 10.8 carats, leaving doubts over whether the model can apply to smaller or lower-quality stones.

Another concern lies in price determination. HB Antwerp estimates polished values using “advanced scanning technologies,” then adjusts forecasts based on actual polished sales, net of costs and fees. Producers can receive a premium if sales exceed expectations but face downward adjustments if prices fall short.

The debate unfolds against a difficult backdrop for natural diamonds. Weak demand and rising competition from lab-grown stones are eroding revenues. De Beers posted a 44% annual drop in Q1 2025 revenue. Lucara cut its full-year revenue forecast to $150–160 million from $195–225 million.

In response, African producers have launched a joint international campaign to promote natural diamonds and counter synthetic alternatives.

This article was initially published in French by Aurel Sèdjro Houenou
Adapted in English by Ange Jason Quenum