Your guide to turquoise

turquoise

Turquoise is the birthstone for the month of December in western cultures, though in some places blue zircon is also used. It is also considered a mark of friendship, or faithfulness in relationships.

Many people love this stone because of its textured appearance and stunning blue colour. In ancient times it was thought to be a luck charm, which would change colour if the wearer was in danger. However it had been discovered that turquoise can change colour when it comes into contact with certain other chemicals, dust or even skin oils; so it may not always be a sign of impending disaster. As such turquoise pieces need special care and should be kept away from cosmetics and solvents.

The most prized turquoise is called robins egg blue, with the greener shades being less desirable. The other most desirable shade is Bisbee turquoise which has a chocolate brown coloured matrix surrounding the vivid blue turquoise. Like many other opaque gems turquoise is frequently sold by size in millimetres rather than actual weight.

Turquoise is one of the many gems which are frequently treated to improve the colour. Some treatments are quite drastic including the use of dyes to enhance the colour. You may also find “doublets” which are seams of turquoise glued onto a stronger base. These are legal provided it is disclosed at the time of sale. Synthetic turquoise is also available and can be distinguished form the real thing by gemmologists by using some non-destructive tests. Many gems are sealed with wax or resin to give strength. Untreated stones will always command a higher price.

The Egyptians were well known for the use of turquoise in jewellery etc and were also one of the first people to fake the appearance of turquoise in an earthenware glaze called faience as early as 4000 BC. Probably the most famous use of turquoise also comes from Egypt, as the death mask of the pharaoh Tutankhamen was inlaid with turquoise as well as other precious stones.