Rust's adoption in the cryptocurrency sector is massive indeed. Parity Technologies and OpenEthereum is the most well known, but both Stellar Development Foundation and Zcash Foundation (both are among top 30 cryptocurrencies) are rewriting their main node implementation in Rust. I'd say at this point Rust has more adoption than both Haskell (Cardano) and OCaml (Tezos).
Grin is perhaps the first cryptocurrency to be written in Rust, starting in October 2016. Its constant 1 Grin per second emission tries to keep speculators at bay.