(A) Feldspar (orthoclase) (KAlSi3O8. ) It is used in the manufacture of porcelain. (B) Asbestos {CaMg3(SiO3)4} It is used for fireproof sheets, cloths etc. (C) Pyrargyrite (Ruby silver) (Ag3SbS3) It is an ore of silver. (D) Diaspore (Al2O3⋅H2O) It is an ore of aluminium.