A general name given to a large variety of hard, natural resins obtained directly from trees such as Trachylobium hornemannianum and Hymenaea courbaril. Copals are also obtained as fossil resins from Zaire and Zanzibar. The fossil resins are very hard and almost completely insoluble. Copals are diterpenoid resins that contain communic acids, communol, resene and volatile oil. They range in colour from colourless to a bright yellow-brown. The hardest copal resin is Zanzibar. Sierra Leone, Kauri, and Congo are of medium hardness. Manila, and Borneo are soft copals. The oldest resins are the hardest. Copal resins may be purchased as large lumps or small tears. Copal resins were used as oil varnishes in the 18th and 19th centuries but they tend to darken and become insoluble with age. They also have been used in commercial varnishes. Synonyms: Zanzibar; Demerara; Benguela; Sierra Leone; Mozambique; red Angola; white Angola; Congo; kauri; Manila; Pontianak; Madagascar; Accra; Loango; Gaboon; Borneo; Singapore; South American; Cochin; Brazilian; Benin, swamp gum; anime; cowrie. Museum of Fine Arts, Boston (2000). [J. Cassar, R. de Angelis]