Smectite is structural formula of the dioctahedral aluminous species may be represented by (Al2–yMg2+/y) (Si4–xAlx)O10(OH)2 M+/x+ynH2O, where M+ is the interlayer exchangeable cation expressed as a monovalent cation and where x and y are the amounts of tetrahedral and octahedral substitutions, respectively. The frequency at 522 cm1 for smectite is due to AlAOASi deformation. Prolonged exposure to Smectite Clay dust may cause a relatively benign lung disease, though there is a risk of the development of massive fibrosis. Repeated and prolonged exposure to respirable crystalline quartz which may be contained in Smectite Clay dust may cause delayed (chronic) lung injury (silicosis).