The sysblas crate provides minimal CBLAS FFI bindings to the system BLAS.
On Linux, this is assumed to be libblas.so; for Debian-based systems, the
implementation of libblas.so can be selected via update-alternatives.
On OS X, this is just Accelerate.framework.
There are a bunch of other BLAS bindings in Rust;
search crates.io to get an idea.
Some of them are intended as part of a multi-crate workflow separating
bindings and sources
(c.f. https://github.com/blas-lapack-rs/blas-lapack-rs.github.io/wiki).
Others use Cargo features to specify a BLAS implementation of choice
(c.f. https://github.com/blas-lapack-rs/blas-src).
sysblas is less powerful but more no-frills: it assumes you just have
some sort of system BLAS installation, you want to link to it, and you
want a minimal set of FFI bindings to it.