1911 Encyclopædia Britannica, Volume 5… (1911)
“ An opaque white surface is sometimes produced artificially on a red carnelian: this is said to be done by coating the stone with carbonate of soda and then placing it on a red-hot iron; or by using a mixture of potash, white lead and certain vegetable juices, and heating it on charcoal. Inscriptions and figures in white on red carnelian (“burnt carnelian”) are well known from the East. Much carnelian comes from India, being mostly derived from agate-gravels, resulting from the disintegration of the Deccan traps, in the neighbourhood of Ratanpur, near Broach. ”
