What Is Importance Of Quarry Dust In Mould Of Blocks

The base of pastel chalks is calcium sulfate caso 4 , which is derived from gypsum caso 4 -2h 2 o, an evaporite mineral formed by the deposition of ocean brine it also occurs disseminated in limestone.Chalk and dehydrated gypsum thus have similar origins and properties.Pastels also contain clays and oils for binding, and strong pigments.