This is Orly FX Intergalactic Space:
this set of polishes came out of the rage for galaxy manis from a few years ago. (Although actually I saw a post about galaxy manis on Twitter just today so it's not like they're gone!) Anyway, this one is a mixed glitter with mostly bronze and purple pieces, and maybe a couple more colors of very fine glitter pieces - plus the big white ones - in a black base. It's really quite awesome, although really I could do without the white pieces and so I just don't worry about whether I'm getting many of those on the nail. The purple/bronze combo is really nice, though, and I can't think of any other polish that's very much like this.
Availability: this (and most of the other FX polishes, apparently) are still showing up on Orly's website, so I imagine you should be able to find this in a wide range of places.