Manufacture of refractory products

2391 Manufacture of refractory products 2392 Manufacture of clay building materials 2393 Manufacture of other porcelain and ceramic products 2394 Manufacture of cement, lime and plaster 2395 Manufacture of articles of concrete, cement and plaster 2396 Cutting, shaping and finishing of stone 2399 Manufacture of other non-metallic mineral products not elsewhere classified