Yielding a lower ore grade in the September quarter, uranium explorer Energy Resources of AustraliaLtd (ASX: ERA) announced on Wednesday that it would have to pare down its production guidance for the year 2010.

The Northern Territory mining firm revealed that its uranium oxide output for the September quarter improved by 10 percent from the June production though the quarterly result fell short by up to 35 percent when compared to numbers posted in the corresponding period last year.

ERA added that while mill head grade saw improvements in September, the levels registered for the quarter were inferior as against the 2009 marks attained by the company, forcing it to move for a downgrade on its expected 2010 uranium oxide production from 4,700 tonnes to 3,900, also previously set at 4,300 tonnes.

In order to meet its 2010 sales commitments of an estimated 5,000 tonnes, ERA would need to buy for more supplies that the company said would substantially offset its 2010 earnings.

ERA explained that "the small price margin associated with the sale of the purchased material is more than offset by the ongoing costs of operation."

After its works in the Ranger mine pit has been interrupted by the unusual heavy and protracted downpours during the past few weeks, ERA said that its mining activities in the area has been resumed while the instability identified on the south sector of the pit has been removed.

The uranium miner is 68 percent owned by giant mining firm Rio Tinto Ltd.

As of 1120 AEDT On Wednesday, ERA shares were trading down by 80 cents or 5.53 percent to $13.66.