Where sapphire gets its blue tint mainly from iron, rubies get their pink to blood-red hue from chromium. So [NightHawkInLight]’s recipe starts with aluminum oxide grit-blasting powder and ...

Padley, P. J., thesis Univ. Cambridge (1959). Dobbins, R. A., Eleventh Symposium (International) on Combustion (Berkeley, 1967).

A browse through images of chromium compounds on Wikipedia shows a whole spectrum of colours: dark red chromium(VI) oxide, orange-red lead chromate, bright yellow sodium chromate, brilliant chrome ...