Mineral
Corindón
Al₂O₃ · Óxidos
Red variety of corundum, coloured by chromium and modulated by iron. Its hardness (9 on the Mohs scale) and lustre make it one of the most valued gemstones. In Malagasy specimens, the violaceous or pinkish tone is due to the Fe³⁺/Cr³⁺ ratio, giving them a cooler appearance than Burmese rubies.
Etymology
From Latin "rubeus", red. The term "ruby" is reserved for red corundum, while the blue varieties are called sapphires.