An Encyclopaedia of Indian Archaeology v1.c21.s6.2

v1.c21.s6.2

The body of the objects has a coarse granulated texture with angular grains of quartz embedded in a clear matrix. Their physical parameters show that they have a concoidal fracture and a greasy lustre, with a hardness of 6 to 7 and a specific gravity of about 2·8. Traces of glaze and enamel (opaque glaze) are sometimes seen on the surface. They have different colours-white, green, greenish-white and bluish-green with green and blue glaze. There is a very high percentage of silica (above 80%), a small quantity of lime and a very low proportion of alkalies, with oxides of copper and iron used as tinctorial agents. The raw material is generally curshed quartz or very fine angular quartz sand. It seems that powdered silica or quartz sand was mixed with a little lime, moulded into shape and fired at a high temperature, when the fusible fluxes (lime, oxides of iron and copper and alkalies) flowed through the sand grains and embedded in a clear matrix. Some objects are decorated with a soda-lime glaze of green or blue colour. They body material was also sometimes coloured. Microscopic examination shows that the objects were sometimes finished smooth with a sharp instrument, as evidenced by regularly oriented striations and scratches on the surface.