Separation of quartz from loess in luminescence dating

When quartz fraction is cleaned of feldspar grains by etching in concentrated HF for 40min,more quartz fraction is etched away,and this method may be not suitable for the purity of quartz in loess.As quartz fraction in loess is separated by the tedious process of etching with fluorosilicic acid for about 6 days,20ml 30% fluorosilicic acid per gram,not only the feldspars in loess can be removed completely, but also less quartz is etched away.The purification of quartz can be checked up not only by IRSL,but also by 110 ℃ TL peak of quartz.