Amber is tree resin that has become fossilised over millions of years. This tree resin hardens into a fossil during a long process of polymerisation and oxidisation. The resulting amber can be yellow or orange and may contain remnants of other organic material, such as trapped insects. Amber is valued as an inexpensive gemstone with a beautiful translucent colour and smooth finish. A crack running through a piece of amber can ruin its appearance if it is not properly patched.
Place the piece of amber on a steel tray and heat in the oven until the stone reaches around 93.3 degrees C. Remove the stone from the oven.
Apply epoxy resin into the crack beginning on one side of the crack and slowly applying the resin until it fills the entire crack. The heat of the rock will make the epoxy thinner and allow it to more easily coat and fill in all parts of the crack. Allow the epoxy to dry overnight.
Sand the uneven surface of the epoxy-filled crack with fine-grain sandpaper until it is level with the surface of the stone. Rub the surface of the stone with a cloth and gemstone polish to smooth out the surface until the crack blends in with the rest of the stone.