Gold prices have weakened this week, and gold on the December contract was down 1.3% over the last five trading days at $1,716 when 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 performance of the $63 billion SPDR Gold Trust ETF (NYSE: GLD) dropped below that of its underlying commodity this week, and was down 2.18% to $166.34 over the last five trading days when U.S. markets opened on Thursday. Similarly, the London-listed Gold Bullion ETF (LSE: GBS.L) lost 2.8% to $165.86 over the same period. Both funds are up around 9% 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 month's biggest risers.

Condor Gold (LSE: CNR.L) climbed 11% to 186 pence this week as investors welcomed the news that the Nicaragua Department of Mines has approved the transfer of the La Mojarra Concession to Condor's Nicaraguan subsidiary. The addition of La Mojarra adds a further 27 square kilometers to the company's La India Project, which now totals 194 square kilometers. Condor believes that that it is "highly conceivable" that the gold mineralization in the La India vein in an adjacent concession continues into the La Mojarra concession.

Shares in Fresnillo (LSE: FRES.L) gained 2.1% in trading to 1,929 pence this morning, capping a 40% gain over the last three months. Fresnillo gained this week after the company announced it had approved a feasibility study for the development of its $500 million San Julian silver-gold project. The project is expected to produce 40,000 ounces of gold and 9.6 million ounces of silver per year when it reaches full capacity.

Finally, shares in Randgold Resources (LSE: RRS.L) (Nasdaq: GOLD) inched up today to 7,440 pence, adding to a 39% gain over the last six months. The company announced today that two giant mills, each weighing 170 tonnes have now been landed at Mombasa port and are being trucked 1,800 kilometers across Africa to Randgold's giant Kibali gold project. The mills will process a total of 7.2 million tonnes per year.

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Roland Head does not own any shares mentioned in this article. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.