A young woman and her fianc choose their wedding rings at a department store in Beijing. More couples are marrying during the National Day holiday and Mid-Autumn Festival, which is contributing to brisk diamond sales in China. [Zhang Wei/China Daily]

Millions of Chinese couples rushing to tie the knot during the National Day holiday have sparked a boom in the diamond industry, which remained subdued outside the country.

Riding on the peak season for weddings, Toronto-based diamond jewelry brand David Seno in Shanghai watched sales balloon after June.

"Diamond rings sold very well in recent months in our store, and the 0.5-carat to 0.7-carat diamonds are the most popular," said Zhang Qing, general manager of David Seno's Shanghai boutique.

Indeed, the jewelry boutique, which opened last December, turned a profit just a few months later, thanks to a rising penchant for diamonds among young couples in China.

The Shanghai Wedding Trade Association estimated that more than 40,000 couples would have their wedding ceremony during this year's National Day holiday -- the highest in three years.

"A diamond ring in my heart means eternity and will make me shimmer on my bridal day," said 25-year-old Dai Xiaodan, who planned to hold her wedding ceremony on Oct 6 in a modern five-star hotel.

Dai will be wearing a 0.7-carat diamond ring worth 20,000 yuan purchased at a traditional jewelry shop, Laofengxiang of Shanghai.

Figures from the Shanghai Diamond Exchange, the country's only stock exchange for diamond trading, showed China's imports of polished diamonds rose to a record high of $300 million for the first six months of this year, up 12.7 percent from the same period last year, making China the third-largest diamond consuming country in the world.

By comparison, the Antwerp World Diamond Center reported that polished diamond imports in Belgium, which holds the world's largest diamond trading center, declined 38.8 percent to $4.5 billion in the first half.

"China's diamond industry has been buoyed by robust retail sales arising from the booming stock market and wedding craze among young people," said Yuan Wenyao, vice president of the Shanghai Diamond Exchange

The price of polished diamonds worldwide dropped 30 percent last August and October as the demand for luxury goods like diamond shrank in the wake of the global financial crisis.

But China is a relatively stable consumer market for diamonds, and the anticipated wedding rush is likely to keep diamond imports rising, Yuan said.

David Seno's Zhang said: "We're confident we will have 15 percent sales growth next year, and we plan to open five to six stores across China in the next three years."