Dr. Martin Knoll holding a sample from the baltic amber collection.

Dr. Martin Knoll of the Department of Forestry and Geology with one of the fossil-bearing amber samples from the Sewanee collection.

Amber is a natural fossilized tree resin that shows conchoidal fracture, has a melting point of 200 to 380 degrees centigrade, and has a hardness of 2 to 3. Amber originates from the chemically complex resins produced by the parenchyma cells of conifers (although angiosperms may also produce some resin). After deposition and burial, resin undergoes prolonged oxidization and polymerization in the presence of sea water to ultimately form amber. Trees extrude resin as a means of healing wounds caused by events such as breaking of branches or boring by insects. While resin is extruded animals and plant matter may become trapped in the sticky material to eventually become preserved in the amber. Such fossils are little altered from their original state, except that the soft interior tissue has decayed to form a fluid and leaked from the body. These fluids often combine with the still fluid resin to form a white emulsion on the outside of the body of the organism. Heating by sunlight has usually caused this emulsion to escape the amber on the side of the body facing away from the tree trunk. The tree-facing side of the body, however, often retains the cloudy emulsion.

One of the unique features of Baltic amber is the presence of stellate hairs from oak trees. These are small, radially branched growths that cover portions of flowers and leaves. Their presence is often interpreted to indicate resin formation during the spring of the year.

The amber formed in a northern German forest during the Eocene Epoch, approximately 50 million years ago.

Contact Dr. Martin Knoll at mknoll@sewanee.edu