1. Any occupation involving—
(a)the mining, quarrying or working of silica rock or the working of dried quartzose sand or any dry deposit or dry residue of silica or any dry admixture containing such materials (including any occupation in which any of the aforesaid operations are carried out incidentally to the mining or quarrying of other materials or to the manufacture of articles containing crushed or ground silica rock);
(b)the handling of any of the material specified in sub-paragraph (a) in or incidental to any of the operations mentioned in that sub-paragraph, or substantial exposure to the dust arising from such operations.