Amber is a stone made from fossilized tree sap. Some pieces of amber have little insects in them that have been fossilized with them.
Role in Guardians of Ga'hoole
Bubo, the Great Tree's blacksmith, calls amber "Fool's iron" because flecks magnetize to the amber, as they would to iron. An example is in The Shattering, where Primrose trades a few turquoise chips for a piece of amber from Trader Mags shortly before she is kidnapped by the Pure Ones. In the hollow where she is kept, a nest of moss, where she is forced to sleep, has flecks put inside. To prevent from being shattered, she rubs the amber on her chest, creating static, and the flecks magnetize to it.