BEIJING, Feb. 1 (Xinhua) -- Lock-up shares worth about 291.3 billion yuan (about 42.5 billion U.S. dollars) will become eligible for trade on the Shanghai and Shenzhen stock exchanges this month.

About 20.5 billion shares will become tradable in February, a relatively large volume that will put pressure on the stock market, according to a report in China Securities Journal.

Shaanxi Coal Industry Company Ltd. will see the unlocking of 7.29 billion shares, the largest group to hit the market on Friday, the first trading day after China's Lunar New Year.

Under China's market rules, major shareholders have to wait one to two years before they are permitted to sell their shares.

China's key stock index, the benchmark Shanghai Composite Index, concluded the Year of the Monkey at 3,159.17 points. The smaller Shenzhen Component Index closed at 10,052.05 points.