Minerals and Metals in Ancient India v2.c47.136

v2.c47.136

*Flint* and *Chert* are related to chalcedony. Sandstone is quartzsand conglomerate rock. Opal is amorphous colloidal silica in massive form. Luster vitreous to resinous. Play of colour. Thin curved lamellae of particles in the matrix have differential refractive indices and cause play of colour on rotation. Cacholong is opaque, bluish white or porcelain white opal.