At first only the blue variety was called sapphire, and corundums of other colors (with the exception of red) were given special, misleading names, such as “Oriental peridot” for the green variety or “Oriental topaz” for the yellow type. Today corundums of all colors except red are called sapphires. Red varieties are called rubies. The various colors of sapphire are qualified by description, i.e. yellow sapphire, green sapphire. Sapphire without additional qualification refers to blue corundum. Orange pink sapphire is called paradschah (Sinhalese for “Lotus Flower”).
There is no definite demarcation between ruby and sapphire. Light red, pink or violet corundum are usually called sapphires, as in this way they have individual values in comparison with other colors. If they grouped as rubies, they would be stones of inferior quality. Coloring pigment in blue sapphire is iron and titanium; and in violet stones, vanadium. A small iron content results in yellow and green tones: chrome produces pin. The most desired color is pure cornflower blue.
Hardness is the same as ruby and also differs in different directions (an important factor in cutting). There is no fluorescence characteristic for all sapphires. It varies to color and source area.

*info by Walter Schumann “Gemstones of the World”