Opal

Opal

Properties

  • Mineral: Hydrated Silica
  • Chemistry: SiO2nH2O
  • Color: All colors
  • Refractive index: 1.37-1.47
  • Birefringence: None
  • Specific gravity: 2.15 (+0.08, -0.90)
  • Mohs Hardness: 5 to 6.5
  • Phenomenon: Play of colour

About Opal

Opal is a hydrated amorphous form of silica. It it is a mineraloid, meaning that it does not have any crystalline properties. Its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock. The internal structure of opals makes it diffract light, and the colours it displays shift as your viewing angle changes. A phenomenon called play of colour. Opals may be white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Opals may display a myriad of different colours and any possible combinations of colours. It varies in transparency from opaque to semi-transparent.

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Product Description

History

The origin of the name “opal” is still debated by historians. Opal may have originated from the Roman word “opalus,” the Sanskrit word “upala” or the Greek word “opillos.” Opals were believed to possess the luck of many different gemstones because of its multi coloured nature. Therefore people from the old days believed wearing opals will bring them good luck..

Sources

Opal is the national gemstone of Australia. Australian produces up to 95-97% of the world’s supply of precious opal, with the state of South Australia accounting for 80% of the world’s supply. White opals makes up 60% of opal production, crystal opal or pure hydrated silica makes up 30% of the opal produced, 8% is black and only 2% is boulder opal. Ethiopia is another important source of opals since its discovery in the early 90s. Opals found there it closely resembled the sedimentary opals of Australia. Other opal producing countries include Czech Republic, Slovakia, Hungary, Turkey, Indonesia, Brazil, Honduras, Mexico, Peru, Guatemala and Nicaragua.

Quality

Top quality opals display vivid play of colour with a translucent to opaque body. Opals come in several varieties which include white opals, crystal opals, fire opals, black opals and boulder opals. Black opals are the most valuable. In terms of colour, flashes of green and orange are common. Blue and the rarest red flashes of colour are more highly prized.

Trivia

The largest opal ever found The Olympic Australis Opal weighs in at 3.45 kilograms.

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