An ant encased in amber, the name for fossilized tree resin. Amber has been known since at least the fourth century BC and was used as fuel in ancient times, as well as jewelry, a use which continues to this day. The Roman naturalist Pliny the Elder correctly theorized that because insects and other objects were occasionally found in amber, it must have been a liquid at some point in the past.
Baltic amber, with an insect fossil inclusion (dated 30+ million years old).
Charoite Chatoyant Rare Purple Russian Stone by FenderMinerals, S)