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Image source: Barrick Gold.

The stock market hasn't made too much headway so far in 2016, with major market benchmarks like the S&P 500 and the Dow Jones Industrials posting gains of just 2% to 3% on the year. However, the beauty of investing in individual stocks is that you can look for companies that have far more promise than the average investment. Smart picks can produce amazing results, and several stocks have managed to double shareholders' money in just the first five months of the year. Below, we'll take a closer look at three of them and explain whether there's more potential profit for those who are only now discovering these stocks.

Cliffs Natural Resources

Commodities stocks like Cliffs Natural Resources (NYSE:CLF) have gotten hammered in recent years. Sluggishness in global macroeconomic activity has dramatically reduced demand for steel and other products used for construction and infrastructure development. That in turn has made the raw materials that go into steel production, including iron ore and metallurgical coal, lose value in sympathy. As a major producer of iron ore in the Great Lakes region, Cliffs Natural fell prey to poor industry conditions, and the stock lost nearly 80% last year.

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Image source: Cliffs Natural Resources.

Since then, however, Cliffs Natural has enjoyed a rebound, soaring more than 175% since the beginning of 2016. A big part of that success has come simply because iron ore prices have staged a rebound. However, Cliffs has also made some smart financial moves that have improved its long-term prospects. A bond swap early in the year was the latest in moves to restructure its debt, and strategic asset sales have allowed Cliffs to focus on its most lucrative opportunities going forward. Most recently, an updated supply contract with global steel giant ArcelorMittal lifted the stock by more than 40%, as investors especially liked the minimum purchase amount of 7 million tons and the ability to provide 3 million tons more.

In order to make good on its potential, Cliffs Natural needs to see market conditions improve to take full advantage of its sales opportunities. If that happens, though, then Cliffs shareholders could enjoy even larger gains in the future.

Barrick Gold

The downward trend for gold-mining stocks has been even longer, and Barrick Gold (NYSE:ABX) has dealt with falling precious metals prices for several years. Ever since gold hit its peak above $1,900 per ounce in 2012, Barrick has struggled to hold its own, and the plunge in bullion prices sent Barrick's shares down as much as 90% over a four- to five-year time span coming into 2016. So far this year, however, Barrick has bounced back, as the price of gold has jumped by nearly $200 per ounce to around the $1,250 range. Barrick shares are up more than 150% so far this year.

One huge advantage that Barrick Gold has over most of its competitors is that its costs of production are among the lowest in the industry. According to recent reports, Barrick believes that its all-in sustaining costs are somewhere between $760 and $810 per ounce. By contrast, some higher-cost producers are struggling above the $1,000 mark, and even with the rebound in the price of gold, that leaves a lot less breathing room than Barrick has in making a profit from gold production.

What helped Barrick succeed was the discipline to sell off non-core assets, improve its internal efficiency and productivity, and get its debt under control. Even though the miner still faces plenty of challenges with gold well off its historical highs, investors are more confident in the long-term prospects for the gold market and for Barrick in particular.

Quad/Graphics

Quad/Graphics (NYSE:QUAD) isn't in the commodities business, but it has also seen some impressive share-price gains. The company focuses on providing print and marketing services to those looking to use various media channels to boost exposure for their own products, services, and content. Last year, the stock fell more than 50%, and Quad/Graphics announced plant closures and job cuts in an effort to try to turn its flagging business around.

Yet by early in 2016, investors were more confident in Quad/Graphics. The company said it had completed its $100 million cost-reduction plan early, and expectations for stronger financial results helped give shareholders hope that the worst was over for Quad/Graphics. In its first-quarter financial report, Quad/Graphics reported slightly lower sales than it did in the first quarter of 2015, but it turned around a year-earlier loss by posting a modest profit of $0.08 per share.

Looking forward, Quad/Graphics has recovered most of the ground it lost in 2015, and so some shareholders justifiably believe that the stock price might pause. If the company can keep producing impressive growth, however, then further gains might be possible for Quad/Graphics shares.

Stocks that double in value are rare finds, and it can be dangerous to jump in after a big upward move. For these three stocks, understanding the potential upside that still remains is crucial if you want to make a smart decision about whether to invest now.

Dan Caplinger has no position in any stocks mentioned. The Motley Fool owns shares of Cliffs Natural Resources. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.