Several publicly listed Bitcoin mining firms in North America have hoarded over 20,000 BTC, worth over $1.1 billion at current prices. As per the data, Riot, Marathon, Bitfarms, Hut8, Greenidge, Argo, and HIVE have collectively mined over 6,463 BTC in Q3, which is 7.5% of the total BTC block rewards up for grab during the period.