A man has been sentenced in San Diego, California, for conspiring to sell drugs over dark web markets for cryptocurrencies.

Thirty-nine-year-old Sky Justin Gornik had pleaded guilty to using a number of marketplaces such as Alpha Bay, Trade Route, Abraxas, Evolution, Outlaw Market, and Dream Market to deal in fentanyl, carfentanil, ketamine, oxycodone, amphetamine and other drugs under various pseudonyms, according to a Department of Justice announcement on Monday.

In a raid on Gornik's home, law enforcement agents seized 1.7 grams of carfentanil and sheets of fentanyl gelatin tablets on June 7, 2017, court documents say. The amount of carfentanil – a super-potent synthetic opioid – found reportedly equated to "over 86,000 fatal dosages."

Gornik was found to have been buying 600-1,200 fentanyl gel tablets a week over around two years from another dark web dealer, identified as Oklahoma resident Steven Wallace George. George has been prosecuted by federal authorities in his home state for manufacturing the fentanyl tablets from pure fentanyl obtained from China.

With his guilty plea, Gornik also agreed to forfeit "millions of dollars" in cryptocurrencies including bitcoins, stratis, ethereum and monero accrued as part of his drug trading. His crypto holdings were held in accounts at the U.S.-based Bittrex and Poloniex exchanges.

"Gornik admitted that these digital or crypto currency represented drug trafficking proceeds of the offense and were involved in the offense of money laundering over the Dark Web," according to the Southern District of California Attorney's Office.

Gornik was given a 70-month sentence for the drugs charges and for laundering drug proceeds using digital currencies.

The investigation into Gornik's criminal activities was led by U.S. Postal Inspectors in San Diego with the assistance of special agents at Homeland Security Investigations (HSI).

Juan Munoz, acting special agent in charge of HSI in San Diego, said:

Drugs and handcuffs image via Shutterstock