Oleoresins are natural resins containingessential oils of the plants. Gum resins are naturalmixtures of true gums and resins and arenot as soluble in alcohol. They include rubber,gutta percha, gamboge, myrrh, and olibanum.Some of the more common natural resins arerosin, dammar, mastic, sandarac, lac, and animi.Fossil resins, such as amber and copal, are naturalresins from ancient trees, which have beenchemically altered by long exposure. The syntheticresins differ chemically from natural resins,and few of the natural resins have physicalproperties that make them suitable for mechanicalparts.
