Polkadot is not a mined cryptocurrency like Bitcoin or Ethereum. Instead, it uses a staking system to validate transactions and secure the network. In order to become a validator on Polkadot, you must put up DOTs as collateral. Once you are a validator, you can earn rewards for every block that you help to validate. So, in short, Polkadot cannot be mined in the traditional sense. However, you can still earn rewards for helping to secure the network by becoming a validator.