China’s burgeoning middle class is buying diamonds so quickly that the price of mass-market stones is rising faster around the world than for top-quality jewels affordable only to the super-rich.

Prices for a 1-carat internally flawless top white diamond have gained about 7 percent in two years, while a stone of similar size and color with slight imperfections jumped 24 percent, according to consultant PolishedPrices.com data.

"The Chinese consumer’s fascination with luxury goods has grown dramatically, along with their pockets,” said Angelito Tan, founding partner of Robert, Tan & Gao, a consulting firm on luxury market strategy with offices in Shanghai and Beijing.

The price jump in more flawed diamonds benefits producers such as Russia’s Alrosa, the world’s biggest by volume with 30 percent of output in 2011, and De Beers, the largest by revenue. Chow Tai Fook Jewellery Group, a retailer with a $13.5 billion market value, said its average selling price dropped in the last six months as it sold more pieces.

Even as shoppers go down market in China, the world’s second-largest diamond buyer since 2011, the gap to top-flight stones is still large: A flawless 1 carat top white round diamond would cost about $28,800, according to online retailer Blue Nile, while a benchmark middle-market SI1-category diamond of the same size and color would cost about $7,200.

China’s market was initially fueled by a rich elite pursuing the best diamonds available. As the economy grew, a new wave of buyers emerged, opening the market to lower-quality stones that form the bedrock of U.S. and European demand.

"The cultural taboo of having to buy the finest diamond is broken,” said Anish Aggarwal, a partner at Antwerp, Belgium-based industry consulting firm Gemdax. “Really high-quality was the sacred thing. You needed to buy fine diamonds, there was a snob effect. That has just disappeared.”

About 30 percent of Chinese sales last year were SI diamonds, the favored clarity of the American consumer, up from 5 percent about five years ago, according to producer De Beers. China is now an SI market which is increasingly similar to the United States, said Aggarwal.

"Five years ago, that would have been unthinkable. The whole landscape in how diamonds are sold to consumers in China has changed.”

China surpassed Japan in 2011 to become the biggest diamond-consuming nation behind the U.S. Retail sales of diamond jewelry jumped 18 percent to $9.2 billion in 2011. Sales in India gained 17 percent.

Buyers in those two countries accounted for about 20 percent of global diamond demand in 2011, and that will rise to 28 percent in 2016 as the market grows to $31 billion from $23 billion, according to Anglo American, owner of De Beers.

While Chinese buyers have lowered their threshold, they haven’t dropped to the lowest quality used in jewelry, sometimes called Wal-Mart diamonds because U.S. buyers find them largely in the superstore. “The gap is narrowing,” said Stephen Lussier, executive director at De Beers. “The Chinese are moving into those mid-range goods.”

The broadest category of mass-market diamonds, known in the trade as “commercial,” has advanced 31 percent in the past three years compared with a 6.3 percent gain for the best gems, according to PolishedPrices.com. Mixed diamonds, the lowest grade used in jewelry, have gained 22 percent.