NEW YORK (TheStreet) - In the less than two decades that have followed the launch of the SPDR S&P 500 ETF (SPY) - Get Report, the ETF industry has blossomed in a major way.

Today, over 1,000 funds are available which allow investors to tap into a vast array of market slices including the transportation sector, Canadian energy players, and the global smartphone industry. The popularity of these products has taken off, with total assets breaching the $1 trillion mark in late 2010.

The story of the ETF industry's expansion has been one of investor demand. As individuals have sought to expand their investment horizons and tap into new corners of the marketplace,

State Street

(STT) - Get Report

,

BlackRock

(BLK) - Get Report

, Vanguard and a slew of other fund sponsors have stepped up to the task, offering funds which allow them to easily achieve their desired investment goals.

In an effort to provide investors with new and attractive products, some companies have revisited previously explored regions of the marketplace, creating funds which cut a well-known sector into increasingly thinner slices.

Earlier this week, Global X unveiled its newest product, the

Global X Pure Gold Miners ETF

(GGGG)

. Gold miners are far from an untapped region of the market. On the contrary, with the launch of GGGG, investors now have four separate products aimed at satisfying investor demand for gold producers.

Market Vectors became the first company to launch a product that targets the gold miners when, in 2006, they unveiled the

Market Vectors Gold Miners ETF

(GDX) - Get Report

, which has proven to be wildly popular among investors, growing to over $6 billion in assets.

Like GDX, GGGG provides investors with exposure to a basket of large, liquid gold miners. However, according to the fund's fact sheet, GGGG's underlying index, the Solactive Global Pure Gold Miners Index, focuses specifically on producers which, "generate the vast majority of their business from gold mining."

By comparing the inner workings of these funds, it is possible to highlight some of the areas where the two differ.

Although both funds track approximately 30 companies, the top ten holdings include a number of variations.

Barrick Gold

(ABX)

and

Silver Wheaton

(SLW)

, two of GDX's largest holdings are noticeably absent from GGGG's index. On the other hand, GGGG lists companies such as Ployus Gold and Osisko Mining among its top 10 positions In GDX they are nowhere to be found.

With over 70% of its assets set aside to its ten largest holdings, GDX is the more top-heavily weighted of the two funds. Within GGGG, the top 10 holdings account for less than 50% of its portfolio.

GGGG's dedication to tracking "pure gold miners" comes with added costs as well. Whereas GDX carries a 0.53% expense ratio, investors holding GGGG are charged 0.59%.

Gold remains a closely followed region of the marketplace as investors seek out protection from the various economic and political factors which weigh on today's global markets. While it may prove itself over time, investors should hold off on jumping into GGGG for the time being.

Like any new fund, GlobalX's newest product will take time to gather steam. In the meantime, low trading volume threatens to boost the fund's risks.

The ETF industry remains a relatively young entity within the broader investing world but its evolution has been quick and dramatic. Already, the advent of these products has opened up a vast range of new opportunities for retail investors and, judging by the speed at which new products are being developed and launched, this is a trend that appears set to continue.

Written by Don Dion in Williamstown, Mass.

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At the time of publication, Dion Money Management owned Market Vectors Gold Miners ETF.