Slack stock is surging more than 50% on its first day trading in an unusual 'direct listing'

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Shares of Slack shot up more than 50% within moments of beginning trading on the public markets Thursday.

The workplace chap app listed shares via an unusual direct listing on Thursday, with existing shareholders bypassing the traditional IPO process and underwriters, to sell shares directly to the public. Slack's stock was set to begin trading at a reference price of $26 a share, but quickly surged to $41,90.

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