After a stunning 2015 which saw Sirius Minerals’ (LSE: SXX) share price soar by over 40%, it may be somewhat surprising to see that the company has experienced a strong first third of 2016. In fact, its shares have risen by 24% since the turn of the year and seem to be well-positioned to deliver further gains over the medium to long term.

Positive outlook

A key reason for this is the company’s opportunity to build a major potash mine near York, with the £1bn+ project set to be delivered in two stages and having the potential to return significant levels of profitability in the coming years. Clearly, a black bottom line is a long way off, but with Sirius Minerals having experienced positive results from crop studies for its polyhalite fertiliser, and  aiming towards signing supply agreements, its medium term outlook remains positive.

Perhaps the major risk on the horizon for the company is financing. With investors nervous about the wider resources sector, fund-raising may prove to be more challenging than previously thought. As such, now may not be the most opportune moment to buy Sirius Minerals, but sizeable share price gains still cannot be ruled out if news flow is positive.

Superb potential for gain

Whilst shares in Sirius Minerals have soared this year, fellow resource-focused company Gulf Marine Services (LSE: GMS) has slumped by 52%, as a lower oil price has started to bite. The operator of self-propelled and self-elevating support vessels is forecast to report a net profit which is 18% lower in the current year than it was last year, which is clearly disappointing. However, with earnings forecast to rise by 28% next year Gulf Marine Services could see a step change in investor sentiment over the medium term.

With Gulf Marine Services trading on a price to earnings growth (PEG) ratio of just 0.1, it seems to offer superb capital gain potential. In fact, a doubling of its share price is on the cards and while its outlook is highly uncertain,  and its share price is likely to be volatile, Gulf Marine Services seems to offer a very enticing risk/reward ratio for long term investors.

Substantial resource

Meanwhile, Amur Minerals (LSE: AMC) today announced that the independent resource update of the Kubuk nickel-copper deposit at its Kun-Manie project in Russia has been completed by SRK Consulting. This is the next step towards Amur completing the definitive feasibility study (DFS), with it now set to develop a comprehensive mine design and production schedule. Furthermore, Amur has a substantial resource from which to define reserves for the DFS having doubled the measured and indicated resource at Kun-Manie in the last year.

Looking ahead, Amur could become a highly profitable mining play in the long run and therefore its share price could feasibly double. However, it remains a relatively small and high-risk business, which is still some way off delivering a sustainable black bottom line. And with the mining sector being so cheap at the moment, there may be better risk/reward opportunities available elsewhere.

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Peter Stephens has no position in any shares mentioned. 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.