Mining and quarrying of such materials as gypsum, asbestos, mica, quartz, natural abrasives other than sand, graphite, talc and soapstone, natural gem stones, asphalt, bitumen and all other nonmetallic minerals not elsewhere classified. Peat cutting and digging is included in this group. Also included is prospecting for non-metallic minerals except coal and petroleum and for minerals in general. Establishments primarily engaged in milling, grinding, pulverizing, etc., these minerals are classified in group 339 (Manufacture of non-metallic mineral products, n.e.c.).