21 Fused quartz as a semi-finished product, namely, ingots, tubes, rods, discs, plates and rings all for general industrial and further manufacturing use; Vitreous silica fibers, not for textile use, namely, for use in the chemical, electrical, telecommunication and semiconductor industries; Fused silica as a semi-finished product, namely, tubes, poles, plates, blocks; Slips containing silicon dioxide, in particular slips containing silicon dioxide for coating crucibles