Tephra deposits provide invaluable chronostratigraphic markers through the Quaternary. Recent developments have made it possible to use tephra deposited far from its source in correlation, even when the number of tephra fragments in sediments or ice-cores is very low. However, the chemical characterisation of such crypto-tephra is vital to ensure that reliable correlations are made. In Aberystwyth, the use of laser ablation ICP-MS allows the trace element analysis of individual shards of volcanic glass from tephra deposits. This approach is being refined and applied to tephra from the eastern Mediterranean, New Zealand and Alaska.