Article: Fossil bone recovery from sediment residues by the 'Interfacial Method'
Eric F. Freeman
New methods for the separation of microvertebrate fossils from particulate sediment residues are based on preferential wetting of the bone particles by water-immiscible solvents in aqueous media. Three embodiments of this basic idea are described, two of them involving adhesion of the bone particles to solid or gelatinous materials (polystyrene or high molecular weight hydrocarbons), whilst the third relies on simple two-phase liquid mixtures. The new methods give results which compare favourably with those from conventional techniques of bone-enrichment, and at minimal or negligible cost. In small-scale experiments, efficient separation of bone has been achieved from gangue minerals consisting largely of quartz, limonite, calcite, siltstone, and claystone, and of particle sizes ranging between 1-4 mm and 0-35 mm. Multi-stage separations are possible, allowing one to obtain high-purity concentrates virtually quantitatively from sediment residues of low initial bone content. One such exercise is demonstrated on the large-scale, using 1 kg of quartz-rich sediment residues.The use of a new reagent, sodium hydrogenoxalate, for the digestion of limonitic gangues, is briefly described, as are improvements relating to conventional bromoform density separations.