NEW YORK ( TheStreet) -- Market Vectors hopes the launch of the "junior" miners fund later this year will help draw attention to small- and mid-cap mining firms in the same way that the hugely popular Market Vectors Gold Miners ETF ( GDX) helped to draw attention to larger-cap miners. The prospectus for the fund, which was filed on May 29, 2009, was recently amended to include a new list of fund components. The underlying Market Vectors Junior Gold Miners Index tracks stocks and depository receipts of domestic and foreign companies in gold and silver mining. As gold prices soar to new highs in the U.S., physically backed ETFs like SPDR Gold Shares ( GLD) and iShares Comex Gold ( IAU) and equity-backed GLD have seen tremendous inflows. According to data from the National Stock Exchange, GLD had the highest net inflows of any U.S. ETF during the month of September. ETFs are excellent vehicles to gain exposure to small companies while minimizing security specific risk, but even well balanced ETFs can be volatile. The top two holdings in the Junior Miners ETF Index, Silver Standard Resources ( SRRI) and Coeur d'Alene Mines ( CDE), have market caps of $1.55 billion and $1.7 billion, respectively. Small- and mid-cap stocks tend to be more volatile than their large cap peers, so it is likely that the new Junior Miners fund will be more volatile than veteran GDX. Of course, the fortunes of gold miners are inextricably linked to the trajectory of gold prices. In that sense, the fund offers a not-so-indirect play on gold. Buying this fund gives you exposure that exhibits significantly greater leverage to gold prices than buying the commodity directly. Keep in mind, however, that leverage can cut both ways. If gold prices fail to rise, or if the cost of mining outpaces the rise of bullion prices, these companies will suffer.