The amount of rare earths exported this year is expected to decrease to about 10,000 tons, much lower than the 31,000 tons allowed to be exported under the country's quota system, said a senior industry official.

Ma Rongzhang, secretary-general of the Association of the China Rare Earth Industry, said China exported no more than 5,000 tons of rare earth in the first half of this year.

That puts it on a pace to export less of the materials than it did last year, when it sent 16,900 tons of rare earths overseas. Even then, that amount was only equal to 56 percent of the country's export quota of 30,184 tons.

He said those figures show that the use of quotas to control exports of rare earths out of China do not impede other countries' imports of the materials.

Of the 96,900 tons of rare earths produced in China in 2011, 17.83 percent were exported, according to statistics from China Custom.

Japan bought 56 percent of those exports, the United States 14 percent and France 10 percent, Ma said.

Smuggling is believed to be the main cause of the decrease seen in exports of rare earths. Also blamed are a rise in the materials' prices — which has depressed the demand for them — and the fact that many overseas buyers of rare earths have stockpiled an amount of the materials that is sufficient to meet their needs.