During 1-2 AD, when these earrings were made somewhere in the Ancient Roman empire, they were constructed with hollow 22k gold domes. Inside there was some kind of black goopy resin, or perhaps pitch. This seemed to be a common way of filling/stabilizing hollow jewelry back then. The material had degraded, and after a lengthy restoration these earrings are ready to be worn. Swirly hooks are original to the period - thread them through once, then twice: the s-shape will help keep them in place.