The Probert Encyclopaedia of Rocks & Minerals

CARBUNCLE

Carbuncle is a beautiful gem of a deep red colour (with a mixture of scarlet) . It was called by the Greeks anthrax and is found in the East Indies. When held up to the sun, it loses its deep tinge, and becomes of the colour of burning coal. The name belongs for the most part to ruby sapphire, though it has been also given to red spinel and garnet.
Research Carbuncle