Turquoise is the third December gemstone. It is a very popular stone and is one of the most imitated. It was used by the Egyptians, Romans and Aztecs but the name ‘turquoise’ arose in the 17th century, derived from the French expression ‘pierre tourques’ (Turkish stone) as it arrived in Europe via Turkey, mainly from mines in what was then Persia where it was mined for over 2000 years.
We think of turquoise as being a blue stone, but the colour can vary from sky blue to a greenish blue. Where the turquoise is mined is a strong determinant of colour as Persian turquoise is a sky blue, usually a uniform colour, while turquoise from the US mines has a greenish colour as it contains iron.
In Georgian and Victorian times, turquoise was used a lot in sentimental jewellery containing flowers as the colour was similar to the blue forget-me-not flower. Also, a lot of brooches in the shape of a bow or knot contain turquoise beads. Generally, antique European turquoise jewellery will be set in gold and is often pavé set, that is, small beads or stones set closely together.
I mentioned earlier that turquoise is a gemstone that is imitated a lot, usually because supply is limited. In modern jewellery, a lot of stones like howlite and magnesite are dyed to resemble turquoise. Both are white and have similar veining patterns to real turquoise. But imitations have appeared throughout history, with the Egyptians substituting a glazed earthernware called ‘faience’. From the Middle Ages through to the early 19th century in France, ‘odontolite’, fossilised tusks of mammoths or mastodons, was used. The fossilisation replaced the ivory with greeny blue or gray blue minerals, which were then heated to become blue. Non-French antique jewellery used glass as a substitute, usually in the shape of small beads. It is hard to detect imitation turquoise. However, because turquoise is very porous and can darken and turn greener due to perspiration and access to water, discolouration of turquoise beads is often a good sign in antique jewellery as is is a strong indicator that the turquoise is real and not glass or dyed ivory.