Diamonds, made of carbon atoms, are the hardest natural substance found on ... The red color is caused by traces of chromium. Corundum also forms sapphire in many colors, which generally come ...

He said Gemologists M.J.M. Dharmasekara and Janaka Hemachandra who performed the microscopic examination identified it as a blue sapphire of the natural corundum stamp. “They told me that it is ...