Yancoal Australia, a new firm created by the merger of Gloucester Coal and China's Yancoal, listed on the Australian Stock Exchange Thursday in the bourse's biggest debut in 18 months.

Yancoal Australia, worth some Aus$5.4 billion (US$5.4 billion), debuted at Aus$1.50, describing itself as "one of the largest pure-play coal companies in Australia".

It closed at Aus$1.34 after a slow first session, with only 288,441 shares changing hands.

Yancoal's major shareholder, with 78 percent of stock, is parent company Yanzhou Coal, one of China's largest international mining groups by market capitalisation with listings on the Shanghai, New York and Hong Kong exchanges.

"The listing is the most significant milestone for both Yancoal and Yanzhou," said the new company's chairman Li Weimin.

"Yancoal's listing confirms our commitment to and faith in the Australian coal industry and future development in Australia."

Treasurer Wayne Swan described Yancoal's debut as a "huge vote of confidence" in Australia's resources sector and its wider economy.

The Australian Stock Exchange said it was the biggest listing since Westfield Retail Trust listed at Aus$8.4 billion in December 2010 or rail company QR National the preceding month, worth $6.2 billion.

Canberra gave the Gloucester-Yanzhou tie-up the green light in March and it was approved by Gloucester shareholders last month, paving the way for the newly-merged coal titan, with coal resources of some 3.4 billion tonnes.

The merged company has forecast production of 25 million tonnes per annum by 2016.

State-owned Yanzhou, China's third-largest listed coal company by output, will have to reduce its stake in Yancoal to less than 70 percent by the end of 2013 under foreign investment conditions laid down by Australian regulators.