Abstract: The sepiolite clay deposits of hunan are all confined to the upper members of the Lower Permian Qixia Formation. These deposits may be classified into the marl type, "Ca-Mg shale" type and clay type according to lithology and sepiolite contents.
By means of scanning electron microscopy, this paper deals with the form and mineralogy of sepiolite and its bearings on the main associated clay minerals, as well as the formation and enrichment of sepiolite during weathering and reworking.
Four types of sepiolite are recognized in terms of the occurrence, form and genesis. Sepiolite in marls and Ca-Mg shales is thought to be formed by neoformation; Earthy sepiolite is the weathering products of the sepiolite-bearing rocks; paper sepiolite owes its origin to leaching, and "asbestiform" sepiolite is a kind of The infilling material within vein walls.
Both talc and montmorillonite were derived from sepiolite. The former is usually associated with sepiolite, and its content is inversely proportional to that of sepiolite. The scale, tenor and quality of sepiolite clay deposits are controlled mainly by weathering and reworking.