Australian Gem Opal

Coober Pedy Antique Opal Bracelet
Black Opal
"Pride of Australia" or sometimes called "Red Emperor"

Australian Gem Opal is a form of Silica chemically similar to quartz but not as hard on the Mohs Scale. Opal was first discovered in Australia near Angaston, in South Australia in 1849. Over 90% of the world's Opals comes from Australia.

Opal is formed  as a result of a replacement of the organic material "wood" with opal. The replacement material is called Opal  and consists of tiny layers of silica spheres structured in a regular pattern.  Amber Gemstone is another organic gem and  the result of  biological processes, formed millions of years ago.

Gem Opal Value

Guidelines for determining the price of Opals has been unsuccessful because of the stones infinite variation in color and pattern. The three main factors in fixing the price paid for Opals are:

  • Background Color: Black Opal is more valuable than light Opal.
  • Dominant Fire Color: Red Fire Opal is more valuable than a predominantly green Opal, which in turn is more valuable than an Opal showing only blue color. But Gem Opal is a play of color, the more vibrant the opal, the more valuable it is.
  • Color patterns: 'Harlequin Opal' in which the color occurs in patches. The Harlequin  is  the prize and usually more valuable than 'Pinfire Opal' in which the color is in small specks.

Caring for Opals

Opals need attention just like other precious gemstones. However, do not kill your  opal with kindness; less is more. Simply rinse Opals in fresh water to refresh them, without the use of harsh chemicals, detergents or abrasive cleaners. Use a bowl of  water, not the kitchen or bathroom sink as you don't want your precious opal gem disappearing down the kitchen sink now! Wipe your Opals with a lint free cloth.

Beware - Treated Matrix Opal

Matrix Opal  is treated or "cooked" with a solution of sugar and then sulphuric acid to enhance the color (that tends to diminish in vibrancy over time). If the price looks too good to be true, it most probably is!

Types of Gem Opal

Black Opal - Black body color with features of manganese oxide as host rock. See Aurora Australis Black Opal!

Crystal Opal - Transparent or very translucent.

Boulder Opal - Dark with iron stone as the host rock.

Milky Opal -  Opaque. Mainly found in Coober Pedy, the Opal capital of the world. 

Composite Opals

Doublet - A composite of light natural Opal cemented together on either common Opal or base material.

Triplet - A composite of light natural Opal cemented to either common Opal or base material plus clear quartz or glass.

Synthetic Opal Looks Reptilian

The Liz Claiborne "Lizard-skin" Opal Necklace & Earring Set
Gilson Synthetic Opal Is it a Natural Opal or a Colourful Lizard?

Synthetic Opal is produced in the laboratory and has a similar structure to that of precious genuine Opal.  Gilson Opals are a good example of true synthetic Opals  with colors that closely resemble a natural Opal. 

The following observations though will differentiate between Opal gem and Synthetic or Faux Opal:

  • Synthetic Gilson Opals have what looks like a "lizard skin"  imprint on the surface that's  unmistakable under good light and magnification. 
  • Synthetic Opal generally shows brighter colors, and color patches are often larger than in Natural Opal.

Synthetic Opal has numerous sub-grains that produce a distinctive "snakeskin" pattern.

Synthetic Opal has a more ordered pattern of colors (generally). The reason is because artificial Opal does not duplicate the complexity and intricate pattern of Natural Forming Opal.


"Aurora Australis"   Image Courtesy:   http://www.cooberpedy.sa.gov.au 

"Gilson Opal"    Image Courtesy: http://www.yourgemologist.com/syntheticopal.html

"Pride of Australia"    Image Courtesy: http://www.opalsdownunder.com.au/learn-about-opals/introductory/famous-opals

 

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