It wouldn't need to be salt.
Basically I was initially thinking about a mechanical transmitter, essentially just taking two equal opposite charges and fixing them to the opposite ends of a pole. Then you spin the pole around it's center (like a baton twirler) and it will emit some (mostly dipole) radiation.
Take an identical setup and fix the centers of the two poles together so we have a cross and spin that in the plane of the cross (picture a tire iron), and we should have a decent quadrapole moment and thus some quadrapole radiation (supposing you could spin it fast enough).
This made me consider iterations of this until you've a ring of alternating charges side by side spinning in a circle. Naturally I thought of table salt (some ionic crystal or another). So classically I get that it should radiate, but since it's a bound quantum state I'm not sure? Also, the strongest multipole moment I imagine would be some ridiculously large number for such a setup (probably making the radiation exceedingly weak and hard to detect?).
Sorry no pictures or equations, I'm tired
Anyway, for those interested I was initially considering how the moment of inertia of our initial pole would end up being dependent upon rotation speed.