Abstract: Starting from pegmatitic sand, the invention provides a method of purifying quartz sand, in which the amount of iron is reduced to less than 0.3 ppm, the amount of zircon to less than 1 ppm, and the amount of phosphor to less than 0.2 ppm. Gas nuclei are also removed. The method is carried out by washing with solution which contains at least 15% by weight of HF in water until at least 40% by weight of the quartz sand is dissolved, and washing with a solution which contains at least 20% by weight of HCl in water at a temperature from 5.degree. to 95.degree. C. for at least 30 minutes. In this method, the grains of the sand are freely suspended in an upward stream of the acid. Such quartz sand can suitably be used for the manufacture of very pure quartz glass for use in mercury discharge lamps, in glass fibers for telecommunication purposes (cladding glass), or in semiconductor arrangements.