Short primer on Opals

Alllrighty then ^_^

Opals come in a multitude of "species" (yes thats what the types are refered to) from several continents.

All opals are soft. Above onyx and marble, but way below diamond and sapphires and quarts.

Do not use opals for jewelry that gets abuse. I would not recommend use for everyday wear unless your very careful with them. One hard knock may fracture the stone.

All opals are of a glassy silica composition, the exact analysis of which is easily found on the web.

All opals come in a range of colors from water clear, to red, orange, yellow peach white and pink and sometimes "opalecent" or hazy purplish blue. Opals may be transparent or opaque. The red ones are called fire opals only because of the red base color, and NOT because of any internal brilliance as described below

Some opals display an additional internal refraction of light known as a "play of fire" or a "rainbow flash" This can be VERY dramatic and often will force the price per carat into the stratosphere! These opals are often called "precious opals". they are like solid bits of rock crystal candy rainbows!

Within the above classification there exists many different types of "rainbow flash color". It can be a broad flash across the surface of the gem, it can be a shimmer from within the gem itself, it can be like needles darting one way or another, it can swirl around with long streamers of color, or it can even be hidden until the gem is held in such a way as to allow light to pass THROUGH it, thereby activating an especially strong play of fire known as a "Contra Luz" (Against the Light) display. These Contra Luz opals are rare and desirable.

OPEC...that is...Opal Producing and Exporting Countries ^_^ (some of them)
Mexico
Australia (yes its actually a continent)
Ethiopia
USA
Peru

Some productive areas...
Within Mexico: City of Magdelana and City of Querectero
Within Austalia: Coober Pedy and Lightning Ridge
Within USA: Virgin Vally,Nevada and Opal Butt,Oregon

Opals may form by themselves in parent rock or they may form on or in fossils or petrified wood.
There are also synthetic opals of varying quality. None will compare to the real thing.

Finnished Gems:

May have parent rock included
May be JUST the solid opal material (jewelry grade)
May have additional material added for durablity (doublets and triplets)

If it has some of the parent rock included, it can be called a boulder opal or a matrix opal. it can be cabbed and polished or tumbled. These are used in more economical settings, but they may still be striking. Good for wire wrap. Also used as specimens for rock collections. Generally not terribly expensive

If its just the solid opal material, it may be faceted or cabbed, or left in a natural shape and polished. This is the higher priced material. (Often surpassing Diamond in per carat price) Some lower grade stuff may be tumbled.

If it is a Triplet, it has a very THIN layer of color bearing opal between a stronger backing (onyx perhaps) and a protective lens (quarts, glass) It is bonded together. These offer the durability of glass due to the lens, but the layers may seperate in time.

If it is a Doublet, it has a layer of color bearing opal bonded to a stronger supporting backing.

Colors (without internal rainbow fire)
Common: Red, Orange, Clear, yellow, white Cream.
Less Common: Deep Red, Deep Orange.
Rare: Black or very Dark

With internal rainbow fire:
Common: Red, Honey, Milky,Creamy, Pink.
Less Common: Crystal, Blue
Rare: Black
Rarer Still: Any color with a "Contra Luz" color display

Buying Opals

Opals are rife with flaws and cracks. You pay dearly for sound specimens. Its important to get good ones for jewelry, to give them a fighting chance. They break easy enough as it is. The seller should mention any flaws, if not, ASK!!!!!

If you dont see the rainbow fire in the picture, assume it has little to none. Sellers now know how to capture this effect if not perfectly, at least enough to illustrate it. Most "fire opals" are sold only for the deep red color and NOT the internal luminescents

Opal measurments are by the carat or millimeter. A millimeter is tiny!!! even 10 of the blighted things are pretty small. Get out a millimeter ruler so you know just how small a 10x4 millimeter stone is. Sellers RARELY include a common item like a coin in the picture for a size ref. A 20 plus millimeter stone or jewelry quality is very large...

AND...

Large opals are breathtakingly expensive. Unless you happen on an ignorant seller who does not know what he/she has, you wont fine a large high quality item on the cheep. Beware.

I would expect to pay 20-30 bucks on auction for a 5-6 millimeter stone of good quality.
Buy it Now will be more expensive.

I would expect to pay 200-500 bucks for a 18-22 millimeter stone.

I would expect to pay 2-3,000 (!) for a AAA gem quality 20 millimeter stone.

-Tailfluffs- Hope this was helpful ^_^