23Level 223.1Manufacture of glass and glass products23.2Manufacture of refractory products23.3Manufacture of clay building materials23.4Manufacture of other porcelain and ceramic products23.5Manufacture of cement, lime and plaster23.6Manufacture of articles of concrete, cement and plaster23.7Cutting, shaping and finishing of stone23.9Manufacture of abrasive products and non-metallic mineral products n.e.c.