While gold has been the star investment of 2016 thus far, its 18% gain since the turn of the year may not continue. That’s because US interest rates are on the rise and this could cause non-interest-bearing assets such as gold to lose their appeal relative to their interest-bearing counterparts.

However, this doesn’t mean that gold miners such as Randgold Resources (LSE: RRS) should be avoided. That’s because with uncertainty among investors being high, the gold price could gain some support as many people seek out a hedge or perceived store of wealth. So while gold may not soar, it may not crash either.

This is good news for Randgold and with the company forecast to increase its bottom line by 39% in the current year and by a further 15% next year, investor sentiment could improve over the medium-to-long term. And with Randgold trading on a price-to-earnings growth (PEG) ratio of 1.9, it appears to offer fair value for money given its upbeat prospects.

While the price of gold has soared in 2016, the price of oil has been rather mixed. Clearly, hitting a low of $28 per barrel earlier this year was hugely disappointing for investors in oil stocks, but since then the price of oil has almost doubled. In fact, it now stands at just under $50 per barrel and with there being the potential for further rises over the medium-to-long term, oil-focused stocks such as Premier Oil (LSE: PMO) and Petrofac (LSE: PFC) could be worth buying.

Appealing valuations

That’s particularly the case since both companies trade on relatively appealing valuations. For example, Premier Oil has a price-to-book (P/B) ratio of only 0.75 and this indicates that it has upward rerating potential. This seems more likely with Premier Oil having adopted what appears to be a sound strategy in terms of reducing its costs, becoming more efficient and also adding to its asset base through the purchase of Eon’s North Sea assets.

Similarly, Petrofac trades on a price-to-earnings (P/E) ratio of just 9.1 and for a company that’s forecast to grow its bottom line by 7% next year, this seems rather difficult to justify over the medium term. Furthermore, Petrofac has excellent income prospects, with the support services company currently yielding 5.7%. And with Petrofac’s dividend due to be covered more than twice next year, its potential to raise shareholder payouts at a rapid rate seems to be high.

Of course, the oil and gas sector is likely to be highly volatile over the coming months and there’s the potential for a decline in the price of oil. However, for investors who are able to live with such volatility and focus on the long term, the likes of Premier Oil and Petrofac hold considerable appeal alongside Randgold Resources.

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Peter Stephens owns shares of Petrofac. The Motley Fool UK owns shares of and has recommended Petrofac. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.