Factories in Wuzhou produced 100 billion synthetic gemstones in 2013, nearly 80 percent of the world's total.

Boom times in Wuzhou

Business owners from Hong Kong and Taiwan flocked to Wuzhou in the late 1980s, bringing with them cutting and polishing machines with which one worker could make 100 finished stones a day.

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"The dust and noise made from cutting, chiseling and polishing would be unbearable to workers today," said Meng Ying, who went from being a stone polisher to a businesswoman.

But, she said, "poverty deafened the people. We could not feel the pain when we desperately needed the money."

Nearly 10 years of workshop life has left her with scarred hands, poor eyesight and a curved spine.

Thanks to increased demand in the 1990s, a gemstone worker could earn 3,000 to 6,000 yuan a month in the factories, when the local average monthly income was only 300 yuan.

The locals began importing machines and starting their own family workshops. More than 100,000 people, one-third of the city's population, were employed in 600 enterprises and countless small workshops by the end of that decade, producing 6 billion stones worth about 3 billion yuan each year.

Even some civil servants and teachers quit their jobs and began working in the synthetic gemstone industry.

Most family workshops in the villages and communities ran around the clock to maximize output, causing serious damage to workers' health and the environment.

Older Wuzhou residents still can recall the raspy noise of the cutting and polishing machines that would drive the neighbors crazy.

"Making gemstones was all life was about then," said Wang Ying, secretary of the Wuzhou Municipal Chamber of Gemstone Commerce.

"But were it not for the gemstone industry, many families would have gone to Guangdong as migrant workers. People were happy they could make easy money at home," she said.

Nearly one-third of the zirconias were dumped in rivers, in the waste yard or near farmland in the form of scrap powder. It is estimated that the powder generated each year in Wuzhou amounted to hundreds of tons in the 1990s, when people were excited by the easy profits and had little awareness of recycling

Chen Biankun, artificial gemstone researcher for the Gems & Jewelry Trade Association of China, said: "The workers in Wuzhou did not have basic protection until new equipment was invented several years ago, and the industry's environmental cost over the past three decades is hard to estimate."

A local government spokesman responded that zirconia powder does not decompose easily and would not have entered the food chain.

Foreign investors from Thailand, India, South Korea, Malaysia and Italy joined the bonanza in the mid-1990s, when the Asian financial crisis happened. By 2013, there would be 28 foreign gemstone enterprises in Wuzhou with a total investment of $15.7 million.

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