The jewelry store she ran with her husband for more than 10 years is making an annual turnover of 10 million yuan now.

Zhou isn't the only one in Changle who has made a fortune out of the precious stone. Sapphire trading has created a handful of millionaires and even billionaires in the small county town.

About three hours drive from Shandong's capital city Jinan, Changle is one of the few places in the world with rich sapphire reserves. Its sapphire is characterized by large size, intactness and purity of color. There are also main features that distinguish it from those of other producing areas in the world, such as Thailand and Sri Lanka.

However, local people treated the dark-blue gem as valueless ordinary stones until 1986, when the region was found to boast 450 square kilometers of sapphire-rich land with deposits totaling more than one billion carats.

Since then, gem dealers and collectors from other parts of the country and even from abroad started appearing in the county and tried to buy rough sapphire deposits in bulk at incredibly low prices. The region soon became a collection of privately-owned mines.

"At first we didn't know much about sapphires and we were just so glad that someone wanted to pay for them," said Liu Hongchang from Wutu village. He began to dig for the stones with his fellow villagers in 1999.

The local government started to place restrictions on exploration from 2008 and banned any form of mechanized mining last year, citing concerns about national resource protection. It significantly reduced production and caused the price of sapphires to shoot up.

"There is little supply now. The scarcity makes it more valuable. If the same bag of deposits were sold it would cost at least several million yuan," Liu said, rueful that he had let go some precious stones too early and too easily.

To improve the fame of its sapphires, the county has held a string of promotions across the world in recent years, including the 2010 Press Conference for International Sapphire Fashion Trends in Hong Kong and the Cross-Straits Cooperation and Development Forum for Jewels in Taiwan.

Thanks to these activities, a large number of fine sapphires from Changle have caused a stir among jewelers around the world. They include a 760-carat sapphire in the shape of a drop of water exhibited at the 2010 Shanghai Expo and a 1,764.8-carat stone shown in Hong Kong. It is one of the largest of its kind in the world.

"Increasing numbers of jewelry lovers find themselves attracted to our sapphires and collect them. Some wealthy investors even buy them for speculative reasons because the stock market and real estate are no longer returning the profits they once did," said Cheng Xiaopeng, vice-general secretary of the Changle Jewel and Jade Industry Association, explaining another reason for their rise in value.

However, although the price of sapphires from the county has rocketed in recent years, Cheng said the price is still significantly lower than the international market price.