Sapphire is the name given to transparent corundum. The other well-known gem in the corundum family is ruby. The word sapphire comes from sapphirus meaning blue, but sapphire can in fact also be red, and, in the type known as ‘fancy sapphires’, a variety of other colours as well.

The different colours are determined by the type of impurities that the stones contain. Purple sapphires contain traces of vanadium, while yellow and green sapphires have traces of iron. Pink sapphires contain traces of chromium. White sapphires are in fact usually light gray or brown when they are mined, and are then heat treated to make them clear. Some sapphires display pleochroism and change colour from shades of blue in outdoor light to shades of purple in indoor light.

In India, gems have historically been attributed with supernatural powers, particularly through the association of stones and planets. Blue sapphire is associated with Saturn and yellow sapphire is associated with Jupiter.

Famous sapphires include the Prince Albert Brooch, a huge sapphire which was given to Queen Victoria by Prince Albert the day before their wedding. The engagement ring given to Elizabeth Taylor by one of her husbands, Michael Wilding, has a huge cabochon sapphire mounted on it. Joan Crawford also received a sapphire engagement ring from her second husband, of 70 carats. She was a great fan of sapphires, to the extent that the press called them ‘Joan Blue’ after her. One of her favourite pieces in her extensive collection included a bracelet set with three star sapphires of 60 carats each. Star sapphires are half-dome-cut sapphires with a starlike effect which seems to glide across the surface of the stone, the way the sliver does in a cat’s eye.

Sapphires are usually particularly well-hidden, but have been found in India, Burma, Thailand, Vietnam, Australia, Brazil and Africa.

Cutting sapphires is notoriously difficult, because as well as being hard, the stone must be cut in such as way as to maximize the intensity and solidity of the colour of the stone. Once this is achieved, however, sapphire makes one of the most sought-after and attractive gemstones in jewellery.