Even if your birth month isn't October, you can still rock opal on your engagement ring. It was once believed that opals contain lightning from the sky because of their kaleidoscopic colors. While that may not be true, there's no other gem quite like it. Whether you're a unicorn-lover or an unconventional bride looking to catch eyes, opal engagement rings are a mystical-looking choice that pair nicely with both modern and vintage styles. See 25 gorgeous examples ahead.