The start of a new year could be a good time to refresh your portfolio. Clearly, the performance of a number of resource-focused stocks in 2015 was hugely disappointing and, as a result of this, many investors may be of the view that selling now will equate to less pain during the course of the year.

Of course, there is a chance that commodity prices will fall further and cause mining and energy companies to record declining profitability and lower valuations. However, for long term investors now could be a worthwhile buying opportunity, with valuations being exceptionally low and the prospects for a number of resources companies arguably being better than at face value.

For example, the world’s largest silver producer Fresnillo (LSE: FRES) is forecast to increase its earnings by as much as 81% in 2016. Despite this, it trades on a price to earnings growth (PEG) ratio of only 0.4 and this indicates that its share price has tremendous scope to rise during the course of the year.

Furthermore, Fresnillo has remained firmly in the black in recent years despite a collapse in silver and gold prices. This bodes well for its future performance, since with a rising US interest rate due to be a feature of the macroeconomic outlook for 2016, precious metals prices may struggle to remain stable. And, with Fresnillo expected to more than double its dividend in 2016, it sends a clear message to the market that it is relatively confident about its financial prospects, which could boost investor sentiment moving forward.

Also offering excellent value for money is industrial services provider Cape (LSE: CIU). Its shares trade on a price to earnings (P/E) ratio of only 9 and, even though earnings are set to fall by 4% this year, Cape’s long term prospects remain relatively bright. That’s at least partly because Cape’s business is well-diversified across multiple geographies and sectors, while its increasing focus on maintenance work means that it is less dependent upon the oil price than it was in previous years.

With Cape yielding 5.9% from a dividend which is covered 1.9 times by profit, it remains a hugely enticing income play. Although dividend rises may not be brisk in the short to medium term and its shares are likely to be volatile due to the uncertainty surrounding the price of oil, purchasing Cape now could prove to be a shrewd move further down the line.

Similarly, Anglo American (LSE: AAL) is also enduring a challenging period and, as a result, has implemented a refreshed strategy which seeks to reduce costs and refocus the business on its most profitable areas. As a result, a number of assets have already been sold and dividends have been cancelled for at least the next year as Anglo American seeks to overcome falling commodity prices which are forecast to cause a fall in earnings of 36% in the current year.

Although this fall in profitability would be disappointing, Anglo American’s share price appears to take further problems into account. That’s because the company trades on a forward P/E ratio of 8.4, which indicates that while things may get worse before they get better, Anglo American’s long term investment prospects appear to be relatively appealing for less risk averse investors.

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Peter Stephens owns shares of Anglo American. 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.