With the price of gold now nearly 40% off of its recent peak, some investors see an opportunity to profit from a future gold price rally. While buying physical gold or an exchange traded fund that owns gold is one way to invest in a rally, a potentially more lucrative way is to invest in gold mining stocks. Reason being, these companies have leveraged upside to gold prices due to gold production growth. The three best options, in my opinion, are Barrick Gold (NYSE:GOLD), Newmont Mining (NYSE:NEM), and Goldcorp (NYSE:GG) due to their high grade reserve base and low production costs.

Why Barrick Gold?
As the world's leading gold producer, Barrick Gold has to be under consideration for the best gold mining stock as its size and scale enables it to keep its gold production costs low. For 2015, the company expects to produce 6.2 to 6.6 million ounces of gold at an all-in sustaining cost, or AISC, of $860 to $895 per ounce. That full-year projected AISC is a reduction from the company's first quarter AISC of $927 per ounce, which shows just how focused Barrick has been on getting its costs down. As a result of its low costs Barrick Gold will really thrive as gold prices rise as the higher gold price would significantly boost its cash flow.

The other thing that makes Barrick Gold one of the best gold stocks is its reserve base, which as the slow below shows is the best in the industry.

Source: Barrick Gold Investor Presentation 

What's worth noting is that Barrick's mines have a much higher average ore grade than any of its competitors, including Newmont Mining and Goldcrop.

Why Newmont Mining?
While Newmont Mining's mines aren't quite as high grade as Barrick Gold's, its mines are still well above the peer average and second best overall. Further, the company is also a fairly low cost producer as it expects its AISC to average between $960-$1,020 per ounce in 2015, with its AISC potentially falling to an average of $925 to $1,025 by 2017. Further, the company recently acquired another low-cost miner that expects its AISC to average between $825 to $875 per ounce over the next two years. Because that's lower than Newmont Mining's average cost, the acquisition has the potential to push Newmont's AISC even lower. In addition to that, the company sees the potential to get those costs at least 10% lower through optimization.

The combination of a very strong reserve base with falling AISC means that Newmont Mining is well positioned to drive robust cash flow growth should gold prices meaningfully improve. Further, the company has one of the best balance sheets in the industry as the slide below notes that it owns an industry leading net debt-to-EBITDA ratio.

Source: Newmont Mining Corporation Investor Presentation

It's that strong balance sheet that enabled Newmont Mining to make its recent acquisition. Further, that strength gives the company flexibility to make additional acquisitions, or invest in new mines, as well as provides a safety net should gold prices weaken any further. When we combine all of this, along with the fact that Newmont is the world's second largest gold producer, it makes Newmont one of the three best gold stocks.

Why Goldcorp?
Goldcorp is currently the world's fourth largest gold producer, but what sets it apart from its larger peers is its focus on being a low cost producer. As the slide below shows, Goldcorp is focused on getting its costs down even as its production has grown by nearly one million ounces over that timeframe.

Source: Goldcorp Investor Presentation 

Those low costs aside, Goldcorp also boasts of a strong balance sheet as it has the second lowest net debt as a percentage of its market cap among senior gold producers, beating both Barrick and Newmont. Further, like both of those two gold miners Goldcorp boasts of owning mines that hold an above peer average reserve grade. Add it all up, and Goldcorp is one of the best gold mining stocks.

Investor takeaway
High grade reserves, balance sheet strength, low AISC, and a large scale asset base are the qualities investors should seek in a gold mining stock. The three companies with the best combination of these qualities are Barrick Gold, Newmont Mining, and Goldcorp. This is why investors looking to invest in a gold miner should take a closer look at these three miners first.