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Pike River Coal has found three potentially mineable coal seams under the main Brunner seam it has opened up on the West Coast, and is exploring further.

The company found the low sulphur, hard-coking coal seams in one new exploration hole in the Paparoa Ranges, which were encouraging but did not prove the extent of the coal, chief executive Gordon Ward said.

Based on previous sampling in the area, the coal had been expected to improve to the north, which the latest corehole had confirmed was the case, Ward said.

The Paparoa seams varied in thickness, and held potentially up to 8 million tonnes of recoverable coal, he said. Test results on the quality of coal in each of the three potentially mineable seams were due in a couple of weeks.

The company's 2.3km tunnel under the Paparoa Range, about 50km northeast of Greymouth, reached the premium quality Brunner hard coking coal seam in October.

The new exploration hole was drilled from the surface to more than 250m below the Brunner seam, nearly 2km northeast of the previous hole drilled 20 years ago. The new mineable seams were 2.2m, 3.4m, and 5.4m thick respectively. They appeared to be among those discovered in the older corehole, but were all much thicker.

Any decision will be delayed until after further test drilling over the next 18 months as mining of the Brunner seam advanced.

Shares in Pike River closed down 1c to 97c yesterday.