Bitcoin cash crashed about 20% on Monday after an impressive rally. But, the decline may be just getting started. 

Bitcoin overall is a gigantic bubble, according to Peter Schiff, CEO of Euro Pacific Capital.

"What kept me out of it is understanding that it's not going to work - that bitcoin or any of these cryptocurrencies are never going to be money," Schiff said in an interview with TheStreet. "They're never going to achieve what everybody believes is going to happen. All that's happening now is people are speculating on something that isn't going to happen."

Schiff pointed to the dot-com bust in the early 2000s as an example of speculation that ended up crashing. "I think the same thing is going to happen with all these cryptocurrencies - they're going to collapse," he said.

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Schiff said there is massive inflation among cryptocurrencies, noting that bitcoin isn't the only one. "They keep on creating them one after another - so the supply is going to ultimately overwhelm the demand," he said.

Bitcoin prices are up some 300% since the start of the year trading at $4,019.

Watch the full interview with Peter Schiff:

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