October's birthstone is the opal.
Mesmerising and unique amongst gems, volumes could be written about opals, but we will skip what we don't feel like writing or reading about.

#7181 Art Nouveau opal ring with great play of color.jewelry_ring_845_1-

Opals have been known and recognised for millenia. The Bible talks about a gem that is assumed to translate to opal. The Greeks and Romans had lots to say about these stones and of course, things really hotted up when it came to the 19th century and the Victorians with their vivid imaginations and wild ideas.
It started with a book by Sir Walter Scott that inadvertently persuaded the misguided public that opals were bad luck. It was not his intention, but people can be fools. It took no less than Queen Victoria herself to lead the way and dispel suspicions. She bought opals for her own children and she was the trend-setter par excellence.
Every culture and age has had its superstitions and beliefs about the benefits and sometimes curses of opals. We just see them as gorgeous gems.

Up to the late 1880's, most 'regular' opals were found in what is now the Czech Republic and Hungary. Then, opals were discovered in huge numbers in Australia and there was an explosion of interest in the subject.  Today, this fascination has still not abated -  well over 150 years later. 

So what is so special about opals? 
Well, for the majority of opals, absolutely nothing. They are dull and matte and not worth a 2nd glance. However, some opals have a particular arrangement of silica spheres within their structure and this results in what is called 'play-of-color'. Instead of a homogenous milky appearance, these gems gleam in multi-colors. These are the 'precious opals'. 
With opals, it is all about the color. A great opal is like a diamond, emerald, ruby, sapphire and amethyst all in one. 

Here are the main types of precious opal:

white opals: often milky and boring, but the ones we look for have good play of color - flashing shades of blues, greens, orange, reds and purple. 
black opals: here the body of the opal is dark  - from grey to black. Look for examples with bright shiny play of color. See patterns below.
boulder opals: similar to the more valuable black opals, but attached to an ironstone underside. 
jelly opals: a somewhat transparent opal that looks gelatinous, but may still have a good play-of-color.
Mexican fire opals: a little different to all the others and will be described later.
matrix and blue opals also exist. 
Whatever type of opal you go for, look for intensity of colors.

#6105 Black opal - notice the rare reds.

Black opals are by far the most expensive and while all play-of-colors can be gorgeous flaring and gleaming out of their dark background, look for red. Red adds to the value of any opal.

Today, most opals are found in Australia's harsh Outback.  The places where the opals are found in Oz can be so hot that the locals have built their homes underground - something worth looking at if you ever venture that far. For fun, get permission from the owners of a property to mine for opals yourself. Fabulous black opals are found in Lightning Ridge and their whiter siblings come from the intensely hot Coober Pedy, location of the dug-out homes just mentioned. 
There are sources in Ethiopia and other African locations; Nevada; Mexico and Europe, but they are relatively insignificant. Again with the exception of the Mexican fire opals.

Like fingerprints, no two opals are identical. Not only the colors differ, but the patterning of the colors. Even within the same stone, we often find differences - Turn the opal around to get a good overall impression of the stone - you might find colors are entirely different when seen from different angles. 

#5973 Jelly opal ring. Note play-of-color despite transparency.

Here are the main types of pattern - the way the colors are arranged - in opals. This is the way opals are often described in order to convey the pattern of the play-of-color.  
             Pinfire or Pinpoint: Small, closely spaced patches of color.
             Harlequin or Mosaic: Broad, angular, and closely spaced patches of color that can resemble a mosaic pattern.
             Flame: Sweeping, ribbon-like bands or streaks of color, often reddish, that move across the stone.
             Peacock: Predominantly blue and green colors, reminiscent of a peacock's feathers.  Mined in Nevada. 
             Kaleidoscopic opals: also found in Nevada
Mexican fire opals do not have the kaleidoscopic play-of-color found in other opals. Look for a uniform, screamingly bright orange color. The brighter, the better. Absolutely scrumptious.

#5977 Outstanding Mexican fire opal jewelry set.      

If financial value is a consideration, know that black opals are far more valuable than white. Jewelry with black opals can command serious money just because of the stone, while their lighter counterparts are relatively more affordable. The most desireable color-play is red, which also adds to value.  Most important - avoid flat color that has no sparkle. 
Mexican fire opals are utterly dazzling. Over the last few years they have become increasingly reconised for their rare beauty and prices have risen accordingly.  I love them and when I find a beautiful jewel with a Mexican opal, try to make it mine. Yes, some of them have cost a very, very pretty penny.
#7587 black peacock opal ring with orange flashes.  

                                 

See lots more important fun facts and information about fabulous opals next week in Opals part 2 - post 256b. 

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