Opheffing van pyriet-verkittingen van fossielgruis

Sieved fossil shell grit is frequently attacked by weathering products of pyrite. This may cause severe damage of the fossils by sulfuric acid combined with the formation of concretions that are not soluble in water. Damaging is prevented when samples are dried immediately after sieving, e.g. by hot air or by washing with an inert liquid such as acetone. Concretions can be removed by heating the sample with a mixture of solution of either KOH, NaOH, Na2CO3, NaHCO3 with additional 10% sodiumdithionite Afterwards the sample is washed with an abundance of water, diluted hydrochloric acid and again water. Drying should best be done with acetone, but hot air may do also. Heating of the sample may be done without sodiumdithionite, but in this case NaOH or KOH should be used. However results with dithionite are much better