method for the removal of mica from quartz separates

_____________________________________________________________________________________________ Sediment samples often contain appreciable amounts of mica, a complex group of alumino-silicate minerals with varying chemical composition which have a strong cleavage that results in their platy structure (Klein and Hurlbut, 1993). Muscovite and biotite are usually the most common forms found in detrital sediments. Standard laboratory treatments (Aitken, 1985) to obtain pure quartz or feldspar for luminescence dating do not seem to reject mica minerals. A few studies have described the luminescence properties of mica (e.g. Kristianpoller et al., 1988; Clark and Sanderson, 1994). Not much is known about whether mica is actually a contaminant in luminescence dating studies, in the sense of whether it contributes significantly to the luminescence signals measured from quartz or feldspar. Excess mica can be removed by spreading the sample over statically charged surfaces (e.g. plastic envelopes or beaker surfaces) on which mica particles tend to stick. This, however, has the disadvantage that a considerable amount of quartz is also lost, especially when small grain sizes are used. We describe an effective and simple procedure to remove mica from etched quartz samples using a detergent solution in an ultrasonic bath.