Colloidal and polymeric nature of fossil amber

Fossilized ambers from several geographical origins, copal from the Kauri pine tree of New Zealand and modern white spruce tree resin have been analyzed by the following analytical techniques: dynamic light scattering, optical and scanning electron microscopy, gel permeation chromatography, IR spectroscopy, rheology and viscometry. The results dispute the prevailing view that amber is largely an insoluble, continuously crosslinked, integral polymer network. Rather, the data indicate that a large portion of amber consists of insoluble though solvent-swellable colloidal particles, ranging from submicron to multimicron in size, which can be dispersed in organic solvents such as N,N-dimethyl-formamide. The presence of colloidal particles in fossil amber, copal and even fresh resin suggests a mechanism for resin exudation involving the presence or formation of discrete ‘packets’ of resin, where the surface of each packet has been modified by the interaction with oxygen and water.