Iris Energy's (NASDAQ:IREN) bitcoin (BTC-USD) production was 325 in September, rising from 301 in August, it said Friday. That increase, though, was small compared with its hashrate due to rising mining difficulty.The difficulty of mining is a closely-watched metric in the crypto ecosystem. It measures how hard it is to mine a bitcoin (BTC-USD) block based on the amount of participants and computing power (hashpower) used to mine and secure the blockchain. A higher difficulty tends to lower miners' profitability.For Iris (IREN), its average operating hashrate jumped 24% to 2,729 petahashes per second from a month ago. That, coupled with higher energy costs led to a 6% decline in operating revenue, standing at $6.2M.Elsewhere, the miner, in an effort to raise capital, has recently agreed to sell up to $100M of ordinary shares to investment bank B. Riley (RILY) over the next two years. IREN said it's also looking at an array of growth initiatives such as ongoing organic expansion and potential mergers and acquisitions.Previously, (Sep. 27) Iris Energy boosts mining capacity to over 3.7 EH/s, as expected.