From Sean Goldsmith in The S&A Digest:

"You only need a few of these... heck, you really only need one of these sorts of deals to be set for life."

That's what our friend Doug Casey (one of the richest guys we know) recently told Dr. David Eifrig about a little-known investment he's used to amass a fortune. Doug was talking about "warrants."

Back in the early 1990s, Doug invested in a small mining company called Diamond Fields International. Doug took part in a deal where a group of private investors placed money directly into the company's coffers in exchange for stock.

To entice investors to buy its shares, some companies attach a special contract to each share that allows an investor to buy extra shares at an agreed-upon price in the future. These are warrants.

In Doug's case, he bought 50,000 "units" for $0.25 per unit. It cost him $12,500. Each unit represented one share of stock and one warrant.

Several years later, Diamond Fields found a large diamond deposit in Africa. The stock exploded in value... and so did Doug's warrants. Diamond Fields traded up to $150 a share... a 59,800% gain. But get this... his warrants (which he got for free) were now just as valuable as the stock... which more than doubled his payout. Doug made almost $15 million.

Warrants are commonplace in the small-cap mining sector... These companies don't have access to the credit markets because their prospects are so risky. They attract potential investors with warrants – essentially free stock. Now, deals like Doug's Diamond Fields investment are normally available only to mining insiders... and go to zero more often than not.

But David Eifrig, editor of our new Retirement Trader service, shows subscribers how regular investors can use warrants to reduce risk and maximize their gains while investing in a variety of companies... including blue-chip stocks (Wells Fargo, for example). It's a secret he learned as an elite Wall Street derivatives trader.

Before you scare yourself out of trying warrants, understand these are much safer than regular stock options. In fact, both the U.S. government and Warren Buffett are currently investing in warrants. And you can do the same with as little as a few hundred dollars. Warrants are probably the safest way to gain huge upside potential without taking massive risks.

Crux Note: To learn more about this little-known strategy, click here.

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