Bitcoin stocks gain in premarket as the cryptocurrency approaches pre-halving levels.Riot Blockchain (RIOT) climbs 11% in premarket trading, Marathon Patent Group advances 12%, and Grayscale Bitcoin Trust rises 5.5%.Bitcoin rises 3.2% to $9,578.00, according to CoinMarketCap; that's up 11% in the past three days and recovering much of its pre-halving decline.Coindesk's Omkar Godbole writes that the gains have erased more than 75% of the drop from $10,500 to $8,100 that occurred in the three days to May 10.Godbole points out that a decline in hash rates — the seven-day average dropped to 114 EH/s from the pre-halving high of 122 EH/s — suggests that some miners have scaled back or shut down operations after Monday's halving.That event cut block rewards to 6.25 BTC from 12.5 BTC, making it much harder or impossible to turn a profit with older mining machines.
