Stocks tied to cryptocurrencies such as Advanced Micro Devices (AMD - Get Report) and Nvidia (NVDA - Get Report) have been on fire due to the rise in the underlying asset, until now.

Cryptocurrencies have been crashing after hitting all-time highs, although leading virtual currency bitcoin has been holding up better than that rest. But, to well-known investor Doug Casey, they are just speculative vehicles.

"You have to consider them like penny stocks and treat them that way," he said in the last part of a three-part interview with Kitco News. 'You can't buy them now and look at them as a store of value because they are not.'

Despite a pullback, bitcoin is still up on the year, up over 100% since January, according to Kitco's aggregated charts. However, the well-known gold bug is not convinced. "Just like penny stocks, most of them are burning matches. I think you hold onto them long enough, you will get burned."

That said, Tuesday is a big day for the digital currency. 

Bitcoin is making a split today, but that may not mean investors should, too.

Bitcoin's transaction history and blockchain will fork, giving everyone who stores bitcoins in a participating wallet or exchange an equivalent number of coins in a brand new cryptocurrency, Bitcoin Cash. According to the future's market, Bitcoin Cash will be valued at around $300. Bitcoins are more than $2,800 each, up more than 180% in 2017 to date.

Breana Noble tells you what you need to know.

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