LONDON -- Gold prices have weakened slightly this week, with the December contract dropping by 1.2% over the last five trading days to $1,771.50 shortly after U.S. markets opened on Thursday.

Of course, the only practical way for most private investors to invest in gold is through exchange-traded funds. The $63 billion SPDR Gold Trust ETF has slipped 0.3% to $171.47 over the last five trading days, while the London-listed Gold Bullion ETF has declined 0.2% to $171.02 over the same period. Both funds are up around 12.5% so far this year.

Gold's star performers
Many investors prefer to invest in gold-mining stocks rather than gold itself, as investing in miners offers the potential for leveraged gains on the price of gold. Let's take a look at some of this summer's biggest risers.

Primero Mining (NYSE: PPP) has gained 124% so far this year, providing shareholders with a breathtaking ride and dwarfing the 12% return from investing directly in gold. The company's shares have surged by 34% to $7.23 in the last week alone, thanks to a favorable tax ruling relating to its San Dimas gold-silver mine in Mexico.

AuRico Gold (NYSE: AUQ) gained 21% yesterday to $7.74 after it announced a $750 million sale of some its Mexican assets to Minera Frisco, a company that is 80% owned by Mexican telecom billionaire Carlos Slim. AuRico will use the proceeds to reduce debt and plans to return funds to shareholders -- "about a ballpark figure of $300 million," according to CEO Scott Perry on a conference call yesterday.

Another gold miner that has outperformed the market this year is Pan African Resources (LSE: PAF.L), which is up 42% so far this year and has risen 13% to 17.5 pence over the last three months. The company reported a 68% increase in full-year earnings per share at the end of September, and its recent acquisition of Evander Mines is set to double production -- albeit at the cost of substantial new debt.

Shares versus commodities
This is a key point to remember for commodities investors: Shares in commodity companies have outperformed their underlying commodities many times over for the last 10 years, thanks to their ability to magnify their gains through successful development of new resources. This free report from the Fool, "Ten Steps To Making A Million From The Market," contains some excellent tips on identifying and investing in potential multibagger shares, including resource shares like gold miners. I strongly recommend that you download it now, as it will only be available for a limited time.

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