Mineralogical studies of the perthites of south Sinai alkali granites.

Studied perthites were separated from alkali granites located in South Sinai. the change in the type of growth from grain to grain in the same sample and somtimes in the two sides of a twinned crystal, indicates that the type of perthitic intergrowth depends mainly on the direction of cut rather than the type of intergrowth.