Corundum, to which family the ruby belongs, of any other color than red is known as sapphire. Big rubis are more rare than big diamonds. The sapphire s name is derived from the Greek word for blue, but the precious stone comes in every color, except red. Titanium creates the blue in the sapphire. The persians believed, that the earth rested on a great sapphire, the color of which was reflected to give the sky its blue color.
Big sapphires are rarities.
They often get own names like diamonds. The emerald belongs to the beryll-family, like the aquamarin. It acquires its medium dark to bluish green color from traces of chromium. There are many big emeralds, which are as valueable and famous as diamonds and rubies. Many hundred carats of emeralds are exhibited in the British Museum and the American Mueum of Natural History.