Amber

The Amber is a standalone fossil in the introduced in.

In
After donating the fossil in, its plaque in the museum will read:

"Amber is simply fossilized tree sap, formed and hardened over many thousands of years. Prized for its beauty, amber is often used in accessories such as necklaces and earrings. Amber containing a trapped insect, such as a bee or ant, can fetch a particularly high price."

Real-world information
Amber is a fossilized tree sap which can contain insects, animals, and other organic material. It is used in jewelry, perfumes, and also in some folk medicines.