The guidelines reference cryptocurrency mining in two places, in a section about power efficiency (2.4.2) and a separate Cryptocurrencies section (3.1.5). The former says that apps "may not run unrelated background processes, such as cryptocurrency mining." The latter has five subsections that further describe what apps can and cannot do in terms of cryptocurrency. Wallet apps for crypto are fine, as long as the developer is enrolled as an organization. No apps may mine crypto, unless they process that mining off the device, like in cloud-based mining. Exchanges are fine, too, as long as they are the ones offering transactions or transmissions of currency. Any apps that facilitate ICOs, futures trading or other securities must be provided by established banks, securities firms and futures commission merchants (FCMs). Finally, cryptocurrency apps can't offer currency as a reward for downloading other apps, posting to social networks or encouraging other users to download apps.
Apple isn't the first one to ban direct mining, of course. Google has already banned crypto-mining extensions from its Chrome Web store. The new Apple guidelines likely apply to both iOS and macOS apps.