Zcash’s NU7 network upgrade activated at block 3,543,405, making about 12,224 ZEC—worth roughly $15 million—in its legacy Sprout shielded pool unspendable. The coins have not been burned: NU7 rejects the only transaction format that can spend them. A future upgrade could restore access, but the upgrade specification warns that spending may never be re-enabled.
NU7 cuts the target time between blocks from 75 seconds to 25 seconds, though actual intervals will adjust as mining difficulty changes. It also sets aside 60% of transaction fees for eventual reissuance through mining rewards starting around February 2031, while preserving Zcash’s 21 million ZEC supply cap and halving schedule.
