GDXJ) and the First Trust ISE Global Copper Index Fund ( CU). GlobalX also has a new copper fund with its Copper Miners ETF ( COPX). The company has the silver category all to itself for now. Canada accounts for 58% of the ETF, Mexico, 24%, the U.S., 10%, and Russia and Peru, 4% each. Many of the Canada-based companies have much of their operations in South or Central America. An ETF focusing on one type of metal will have concentrated holdings, as is the case with the Silver Miners ETF. Four of the 25 stocks account for 48% of GlobalX Silver Miners ETF. As such, it's important to know about the larger holdings. Industrias Penoles is from Mexico; Pan American Silver ( PAAS) keeps its headquarters in Canada but has mining operations in Peru, Mexico, Argentina and Bolivia; Silver Wheaton ( SLW) isn't a miner at all -- it buys silver from mines where the metal is produced as a byproduct; and Fresnillo, also a Mexican company. While GlobalX Silver Miners ETF has concentrated holdings, it's still less risky than owning a single silver stock. The ETF is for investors who want to own a niche segment without picking stocks in a very volatile part of the market. Silver-mining stocks are, indeed, very volatile. That can be a good thing or a bad thing. For perspective, the MSCI Canada Index has an annualized standard deviation of 25 versus 49 for the index underlying the GlobalX Silver Miners ETF. The materials sector has a 3.4% weighting in the S&P 500 Index, so investors wanting to add exposure to miners ought to take that into account. A 10% weighting would be a huge bet that would increase volatility dramatically. A 5% weighting would add a lot of return without causing overwhelming anguish in a down market. The ETF could serve as an emerging-markets proxy, given how many of the miners are based in developing countries. The charts for some of the larger holdings in the fund are similar to the iShares MSCI Emerging Markets Fund ( EEM), which allocates 28% to resource stocks.