Teck Resources Ltd (TCKb.TO: Quote) said on Thursday its second-quarter adjusted profit rose 91 percent, largely due to higher coal and copper prices.

However, the company cautioned it expects full-year coal sales to be at the low-end of its forecast range. Teck has been forced to trim its coal production forecasts this year on multiple occasions, due to operational hurdles, labor disputes, adverse weather and other issues.

Last month, the company warned its second-quarter coal sales would be at the low end of its forecast range as Japanese clients have deferred shipments following the earthquake and tsunami.

Vancouver-based Teck is also one of the world's top copper and zinc producers, with mines spread across Canada, Chile, Peru and the United States. The company is also a top exporter of metallurgical, or coking, coal -- a key raw material used in the manufacture of steel.

Canada's largest diversified miner said it continues to expect 2011 coal production costs to fall within a range of C$71 to C$76 per ton with costs trending lower later in the year, as production volumes increase. Transportation costs will remain around C$30 to C$34 per ton.

Teck said the majority of its coal customers will pay about US$315 per ton for its top quality coal in the third-quarter. Average coal selling prices in the period are expected to range between US$280 and US$290 per ton.

Coal sales in 2011 will be at the low end of the 23.5 million to 24.5 million ton range, the company said. It also expects annual copper sales to be in the range of 330,000 to 340,000 tons.

Teck said its adjusted profit in the period ended June 30 was C$663 million, or C$1.12 per share, up from a year-ago profit of C$347 million, or 59 Canadian cents a share.

The higher adjusted profit was driven by higher commodity prices, but these were partially offset by lower coal sales volumes, higher operating costs and the effect of a stronger Canadian dollar.

Including gains from an asset sale and other one-time items, the company said net income in the quarter was C$756 million, or C$1.28 a share. That compares with a year-ago profit of C$283 million, or 48 Canadian cents a share.

Teck's results mirrored those of its larger rival Vale SA (VALE5.SA: Quote). The Brazilian mining giant reported a 74 percent jump in its profit earlier on Thursday.

Quarterly revenue rose 27 percent to C$2.8 billion, on the back of a 30 percent gain in the price of copper and a 49 percent increase in the price of coal. The average price of zinc also rose 11 percent from year-ago levels.

Morningstar analyst Daniel Rohr noted that Teck's quarterly results indicate that its copper production costs ticked higher on a sequential basis.

"The coal sales volumes like Teck said were at the low end of the 5.5 to 6 million ton range, so no surprises on the coal side," said Rohr, adding that Teck's third-quarter coal pricing forecast is also in-line with that of its peers.