… dichroic glass studs.
I bought my first pair of these over the summer. I’d only just lopped my hair off and was fumbling about looking for new earring options. I glimpsed a pair at the Powderhorn Art Fair and was absolutely mesmerized by how they seemed to glow from within. Snapped ’em up, and have bought several Etsy pairs since.
Apparently, dichroic glass contains multiple micro-layers of metals or oxides, and has a particular transmitted color and a completely different reflected color. Hence the glow. It’s really lovely stuff. Behold: