2391INDUSTRI PRODUK REFRAKTORI (TAHAN API)

manufacture of intermediate products from mined or mined non-metallic minerals, such as gravel, stone, or clay; | manufacture of refractory mortar, cement, and so on; | manufacture of refractory ceramic goods, such as heat-insulating ceramic goods from siliceous fossil flour; refractory tiles, blocks, and bricks; and chemical or distillation flasks, crucibles, filters, tubes, and pipes. This subclass also includes | manufacture of refractory products containing magnesite, dolomite, or chromite.