There are still opportunities for investing in commodities despite volatility and a slowing Chinese economy, said Marc Faber, author of The Gloom, Boom and Doom Report.

A slowing Chinese economy might mean less worldwide demand for commodities, since China is the world's largest used of commodities such as copper and zinc.

Prices for commodities like copper may rally, Faber told CNBC, because there are relatively few players in those markets, making them easy to manipulate.

“The markets are very volatile, and it takes a lot of courage to be short,” Faber said.

After China reported that its gross domestic product for the second quarter met investor expectations, copper, as well as oil and gold, rallied on Friday. Plus, investors are betting that China will stimulate its economy, which would boost commodity prices.

Its GDP growth was 7.6 percent, the first it fell below 8 percent since 2009, but Faber told CNBC China is misrepresenting its economic figures and its growth is much lower.

However, Ruchir Sharma, head of emerging markets at Morgan Stanley Investment Management, told CNBC recently that the bull run in commodities markets during the past decade is coming to an end thanks to cooling demand from China.

Raw materials like oil and grains and metals like copper have soared in recent years thanks to voracious demand from once red-hot emerging markets, especially China, although the global slowdown has crimped the need for commodities that fuel global growth.

“China’s growth is downshifting to a lower plain, it’s very commodity-intensive phase of growth is coming to an end. This to me marks a big decade of increase in commodity prices coming to an end,” Sharma said.

Still, hedge funds have put their money — more than 1 million contracts — on commodities on the bet that China will stimulate its economy, prompting the longest commodity rally since February, according to Bloomberg.

“The Chinese numbers are telling us that there will be more easing,” James Paulsen, chief investment strategist for Wells Capital Management, told Bloomberg.

“People realize that the effect of the easing that we saw in some countries will be realized over the next few months. There is a change in the direction of the wind because of a combination of these factors, and probably we are seeing some confidence building.”