The rise in the price of gold has taken most investors by surprise in 2016. It has been up by as much as 17% at times this year and this has had a hugely positive impact on investor sentiment towards gold mining stocks such as Fresnillo (LSE: FRES). And with uncertainty being high regarding the prospects for the global economic growth outlook, it would be of little surprise for the price of gold to move higher as investors seek out perceived safer assets.

Of course, Fresnillo is more often viewed as a silver miner, but even silver has risen by 14% in 2016. Therefore, its shares have risen by as much as 40% since the turn of the year.

Clearly, investors who haven’t bought shares in Fresnillo may be somewhat disappointed at missing out on this gain at the same time as many other shares have fallen. But with Fresnillo trading on a price-to-earnings growth (PEG) ratio of only 0.2, there’s still plenty of upside potential on offer.

While Fresnillo’s future is highly dependent on the price of gold and silver, its margin of safety appears to be sufficiently wide to warrant investment at the present time. That’s especially the case since US interest rate rises now seem less likely, which has historically equated to good news for precious metals prices due to the lack of competition from income-producing assets.

Boosting profitability

Also offering long-term growth potential is copper, gold and molybdenum miner Antofagasta (LSE: ANTO). Unlike Fresnillo, Antofagasta hasn’t benefitted from a soaring price for copper lately (copper has historically accounted for most of Antofagasta’s production), but it’s positioning itself to withstand the current crisis and emerge in a stronger position relative to its peers. For example, it has sold-off its water interests and is focused on reducing costs and improving efficiencies. This should boost its profitability in the long run.

Like Fresnillo, Antofagasta trades on a PEG ratio of just 0.2, so there appears to be considerable capital gain potential on offer. And with Antofagasta increasing production in its most recent quarter (including a rise in gold production of 22%), it seems to have a sound strategy through which to deliver not only improved profitability, but a better diversified business in future years.

Take a look

Meanwhile, BHP Billiton (LSE: BLT) also seems to be worth buying at the moment. It remains one of the best diversified miners in the world, although this hasn’t helped its profitability in recent years since the prices for copper, iron ore and oil have all fallen heavily. The effects of this are still being felt, with BHP Billiton’s earnings due to fall by 88% in the current year. Therefore, investor sentiment may remain weak in the near term.

Looking a little further ahead, however, BHP Billiton’s strategy of cutting costs and restructuring its business could be about to pay off. Earnings forecasts for the next financial year show that pre-tax profit is set to almost double to £2.8bn and this could be the start of improved performance for the business. This rapid rise in earnings puts BHP Billiton on a PEG ratio of only 0.3 which, while higher than the respective figures for Fresnillo and Antofagasta, still indicates that BHP Billiton has a very favourable risk/reward ratio.

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Peter Stephens 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.