Should I top up on mining stocks after today's results?

BHP Billiton (LSE: BLT) reported a stonking $6.4bn loss for 2015/16 this morning. The writedown was caused by a $4.9bn non-cash impairment of its US onshore oil assets and a $2.2bn charge for the clear-up of the Samarco dam disaster.

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However, these should be genuine one-off charges. BHP's underlying earnings present a more reassuring picture.

The group reported an underlying net profit of $1.2bn and generated net operating cash flow of $10.6bn for the year to 30 June. Operating costs fell by $437m and are expected to fall by a further $1.2bn during the current year.

Underlying free cash flow of $3.4bn was enough to cover the final dividend of 14 cents per share, which gives a full-year payout of 30 cents.

At the current 1,050p share price, BHP trades on a trailing P/E of 58 and has a trailing yield of 2.3%. That may not seem very attractive, but it's worth remembering that the mining sector is currently recovering from a major down cycle.

BHP's profits are expected to double to $2.4bn, or $0.48 per share, during the current year. That puts the stock on a forecast P/E of 28, but it would still mean that the group's earnings were 80% lower than those seen in 2013/14.

I believe there's considerable scope for BHP's profits to rise over the next few years. I'm holding onto my shares and believe the stock remains a long-term buy.

Copper-bottomed gains?

Shares in copper miner Antofagasta (LSE: ANTO) rose by more than 6% this morning. A 14.6% fall in the average copper price realised meant that revenue fell by 18.5% to $1,448m during the first half.

However, the Chile-focused firm's net cash costs fell by 17.6% to $1.26/lb. This resulted in earnings before interest, tax, depreciation and amortisation (EBITDA) rising by 2.3% to $571.6m, despite lower copper prices.

Low mining costs have always been a key attraction for investors in Antofagasta. The firm's shares are now up by 59% from their 52-week low of 340p. Further near-term gains may be unlikely, as the firm expects the copper market to remain oversupplied for at least another year. But for investors with a longer-term view, I believe Antofagasta remains attractive.

Silver powers ahead

Shares of silver and gold miner Hochschild Mining (LSE: HOC) rose by more than 9% this morning. The firm cheered investors by reported first-half revenue of $339.3m, a 78% increase on the same period last year. Pre-tax profits were 38.9% higher, at $60.3m.

The gains are the result of a triple-whammy of good news for Hochschild shareholders.

Gold and silver prices have risen sharply this year. Strong performances at the Inmaculada and Arcata mines have enabled Hochschild to increase its full-year production target by 6% to 34m silver equivalent ounces.

Finally, the group's all-in sustaining costs are expected to be $11-$11.50 per ounce, significantly below previous guidance of $12-$12.50 per ounce.

Is Hochschild a buy? This probably depends on how much further you expect the price of gold and silver to rise.

Net debt remains significant at $266.5m, but the group has already repaid $70m so far this year. I'd expect the remaining balance to continue falling this autumn and would probably hold onto the shares in the hope that dividend payments can be resumed next year.

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Roland Head owns shares of BHP Billiton. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.