Rather than focus on the price of gold or the physical possession of gold bullion, GDXs niche is holding publicly traded companies that are involved in the mining of gold and silver. GDX tracks the NYSE Arca Gold Miners Index, which gives GDX access to almost 30 precious metals mining companies around the globe, including some of the industrys biggest names, with a nice blend of small-, mid- and large-cap stocks represented. Note that some of the firms mine other precious metals besides gold, so GDX is not strictly a gold play. Nevertheless, gold is the primary focus of the fund.