Opal: What is it after all?

Opals rough guide and worth

Opal is one of the most beautiful and enchanting gems on earth, mostly because of its origins, iridescences and lights.

There's a huge variety of opals in the world, depending usually on the colours, frailty and iridescence patterns, exactly like the 4 C's for Diamonds (Opals-Quality Factors of the  Gemological Institute of America-GIA). The opal is composed of silica and water: when the water evaporates and precipitates at low temperatures to form layers or nodules of opal in fissures, veins, and cavities of volcanic and sedimentary rocks, it generates some silica deposits; it's a  procedure that protracts during millennia as at the same time is very simple.

​​Colors and lights play together thanks to a particular phenomenon called “diffraction”: Silica veins change the direction of light. When light passes through the gem the result is the rainbow play-of-color. The diffraction grating arrangement creates a play of rainbow sparkling light from within the stone unlikely any other gem; to simplify the concept of this phenomenon you can compare it to the iridescent reflections caused by the grooves of a DVD or CD.

Diffraction in Opals

Opal is the national gem of Australia, 97% of the world's supply of precious opal comes from the Coober Pedy, Lightning Ridge and Andamooka fields in North and South Australia, especially  Black Opals. In Roman times, the primary source of opal was an area in what is now eastern Slovakia. Precious opal has also been mined in Honduras, Mexico, and the Virgin Valley in Nevada, Transilvania, Mexico,Brazil, United States and Ethiopia.In these places  it’s impossible to find opal crystals, but veins or balls, or sometimes solid earth conglomerates. 
Opals, when found, are not so beautiful and colourful: they are just pieces of stone covered with concretion and excavation soil , but at the time of cutting them, the beauty and the preciousness comes out. Stay tuned for the Black Opal follow-up on next blogs.

Unearthed raw Opals

Opal Caves- Coober Pedy, Australia

Opal Characteristics

The gem is quite particular and delicate, low humidity can cause the loss of it's iridescence (polishing may solve the problem) it’s sensitive to extreme temperatures and malleable to work being almost as hard as glass. Because of it's value , the difficulty is on losing as less material as possible during cutting and shaping, maximising control over polishing and cutting errors (cracks, burns etc.)

Opalia owner Mr. Paolo Labianco, opal cutting - Lightning Ridge, Australia

Opalia Shop: Black/Grey Opal - Lightning Ridge, Australia

Opal is considered a unique gem but there are many varieties: the White Opal is the most common one, it’s quite opaque, but veins are really colorful; the Crystal Opal is very bright and coloured like a rainbow, it usually has a translucent base; the Semi-black Opal has a grey base, translucent or opaque and it’s really sparkling; and then the Black Opal is the most precious one, with vivid colors and iridescences, from green to violet, red and gold.​

Opal value

Opals being unique and rare as fingerprints, easy on being detected as false or synthetic, worldwide demand is putting tremendous pressure on opal prices. Opals price range may vary from 2$ per Carat to 20.000$ per Carat, typically depending on origin and Colour, Cut, Clarity and Carat at first, completing estimate with the detection of  play of colour, brilliance, body tone, opals class, pattern, colour bar and faults. 

Nowadays the most expensive opal is the "Virgin Rainbow" which is valued over $1 million and was purchased by the South Australian Museum in Adelaide which will be presenting it as part of their "Opals" exhibit to celebrate 100 years of gemstone mining in the region.
​

Original article on "Virgin Rainbow Opal" Here

Curious About Opalia's Opals? See more