Amber

Amber is fossil resin which has petrified through polymineralization. It's very soft and easily carved by hand. It's a 2-2.5 on the mohs scale. 

First stage of amber is resin leaking from a coniferous tree and hardening. Over time this resin turns to copal. When the copal loses enough oil and polymerization continues and the resin oxidizes. After time, sustained heat and pressure drive off the terpenes, shifting the resin to amber. 

Small pieces of amber which used to be used only in varnish making are now able to be compressed together to make pressed amber for lower priced jewelry and carvings.