Ruby is the name given to red gem quality corundum. All corundum that is not red is called sapphire. Corundum is the second hardest gemstone after diamond, although it is only 1/140th as hard and scratches and chips can occur. Ruby is one of the most popular gemstones for use in jewellery and can be any shade of red, from pinkish or purplish to brownish. The most desirable colour is ” pigeons blood” – pure red with a hint of blue. Ruby is one of the most expensive gems, large rubies being rarer than comparable diamonds. Since the beginning of this century synthetic rubies have been available; these have the same chemical, physical and optical properties of the natural stones. Synthetic rubies are used in watch mechanisms. Inclusions are common in natural rubies and can show the difference between a natural and synthetic stone. Ruby is birthstone for July.