The copals are a class of hard resins used principally in varnish manufacture. They are of various origins, both geographically and botanically. Their principal characteristics are their hardness, high melting point and comparative insolubility unless subjected to destructive distillation. There are three chief varieties: (1) Fossil copal, found in the ground in localities where the trees yielding it have entirely disappeared. (2) Semi-fossil copal, collected from the ground in the neighborhood of living copal trees. (3) Fresh copal, found on living trees, either as the result of natural exudation or from artificial incisions. The fresh copal is of least value and the fossil copal is most highly prized.
East African copals, known in commerce as Ammi gum or resin, are fossil varieties coming from Zanzibar, Madagascar and along the East African Coast. American copals are collected in South America and probably originated from trees related to those which produced the East African copals, although the product is softer. Kauri or cowrie copal or Kauri gum, as it is often called, is found in New Zealand exclusively. M. Kahan has investigated Acera copal and Benin copal (Arch. d. Pharm., 1910, ccxiviii, p. 443) and gives the percentages of the various constituents found.
The Sierra Leone copal is described by Daniell as occurring "in small round tears, or irregular conical and smooth nodulated masses, seldom exceeding in size an ordinary duck egg. They are covered, to a greater or less extent, by a peculiar white efflorescence, which increases by age. Their color graduates from a pale green to a lemon or dull yellow."
