Turquoise

7x5 Oval Turquoise

4.5mm Round Turquoise

General
Tuquoise is an opaque blue to greenish gemstone, a hydrous phosphate of aluminium, with some copper and iron.
It is believed that it got its name from the French word for Turkish (turquois), from a popular misconception that the stone originated from Turkey. This would have been because it was traded in Turkey, by Turkish merchants who had sourced it from Persia. It was also used extensively in Turkey to decorate mosques, palaces, and other important buildings and homes. Turkish dealers sold it to Venetian merchants, who brought it to Europe.
Although it's crystal structure is triclinic, it rarely forms large crystals, and is said to be cryptocrystalline.
It is also usually found with patches of white matrix interspersed, which tends to be less attractive, and reduces its value.

Colour
The colour turquoise is named after the gemstone. The best specimens are a beautiful light blue stone, with green overtones. In general, the more green the stone, the less attractive it is considered.
Unfortunately, turquoise will tend to become greener with age, due to exposure to heat, light, dirt, grease, and chemical attack.

Sources
Historically, most turquoise came from Persia, now Iran, which is still the source of most of the world's best turquoise. It is also found in Egypt, Turkestan, and the USA.

Technical Information

Gemstone Name	Turqoise
Chemical Composition	CuAl6(PO4)4(OH8. 4H20 The copper (Cu) is often partially replaced by Iron (Fe)
Chemical Name	Hydrous Cupro Alumium Phosphate
Hardness	6, Variable 5 to 6
Refractive Index	1.61 to 1.65
Bi-refringence	0.040
Specific Gravity	3.52
Crystalline System	Triclinic, Cryptocrystalline
Optic Sign	Positive
Optical Character	Biaxial

Gemstone	Weight	Shape	Size & Description	Available	Price £	Price $
Turquoise	0.71	Oval	7x5	Yes	£6.00	$Ask
Turquoise	0.39	Round	4.5	Yes	£3.00	$Ask