The term “amber” is a general designation for fossil resins or “petrified” plant sap. The time, conditions and sequences of chemical reactions required for the process of turning resin into amber have yet to be explained conclusively. Only the initial phases of amber formation can be understood on the basis of the resin secretions of contemporary plants. Many conifers and a number of deciduous trees secrete resins spontaneously or as a result of injury. In chemical terms, resins are mixtures of various organic, compounds belonging to the family of terpene derivatives. They are insoluble in water, have a more or less aromatic odor and are initially adhesive. When exposed to air, the viscous resin mass can harden relatively quickly due to the loss of volatile components. Polymerization then follows with the formation of carbon chains. The resin continues to transform and harden for millions of years, during which time the filamentary molecules of the resin mass become progressively “knotted” and the solvents and volatile constituents gradually disappear. The formation of amber could be referred to as a process of maturation, comparable to the carbonisation of plants into brown coal and then hard coal.
The process also includes intermediate forms of different age between resin and amber, which are generally referred to as copals. Copals are often transparent, hard and usually odorless, but “smear” when ground. Typical copals from tropical deciduous or coniferous trees are known from East Africa, Madagascar, New Zealand, Colombia and the Dominican Republic. Africa and New Zealand . in particular used to export copal by the ton for paint production. Studies based on carbon-14 dating have shown that the majority of commercial copals have their origins during the historical age.