HISTORY: Opal, from the Greek, "Opallos" meaning to see a change of color, is a formation of non-crystalline silica gel. Opal is made up of amorphous silica spheres with a little water in the structure. Precious Opal consists of millions of silica spheres of similar size arranged in regular layers. This structure results in the diffraction of light, the wavelengths of white light being separated into the spectral colors. The color produced depends on the size of the spheres. Red, the rarest color, can only be produced when large sphere sizes are present.

Between 85 & 120 Millions of years ago silica seeped into crevices and cracks in Australia’s sedimentary strata. Through eons of time and through nature's heating and molding processes, the silica hardened and can today be found in the form of brilliant opals.

Opal is set apart from other gemstones, because of its characteristic appearance, displaying sparkling prismatic colors which change and flash as you turn the stone in your hand. No two opals are exactly alike!

Australia is the world's most important source of opal. Opals are usually found in sandstone or claystone (called bulldog shale). Deposits are spread over a wide area, and there is little clue to their location

Mining is done on a small scale by individuals (not large companies) with hand-operated machinery and small tools, hand picks, electric jack-picks and of course explosives. The opal miner is a strange breed of individual. He chooses to lead a Spartan life in a particularly barren and dry corner of the world while he searches for his rainbows. To escape the extreme temperatures during the summer about half the miners and their families burrow a home underground in Dugout's.

Because opal displays a whole rainbow of colors, it can be worn with any color outfit. It is usually cut in a dome shape [cabochon] and set in rings, earrings, pendants, bracelets and pins. It may be joined by accents of ruby, sapphire or emerald to enhance particular color flashes in the gemstone. A fine opal piece is often guarded in a web of small diamonds as are other exceptional colored gems. Some opals are fashioned into beads [but they are rare] for a major contribution to a woman's total look.

HOW ARE OPALS VALUED?

Cut and polished opal is priced according to the value per carat (0.2 grams) so that value comparisons can be made. There are 5cts to the gram.

Opal Value is based on the following criteria: color, number of colors, type of pattern, brilliance, perfection of the stone, the cut, the size and unique color patterns or features, and the rarity of the variety of color and or pattern.

PRECIOUS OPAL

Precious Opal is Opal which exhibits the phenomenon known as play of color produced by diffraction of white light due to opal's microstructure. This is composed of an orderly arrangement of spheres of silica in regular three dimensional grid producing colors by diffraction and interference of light waves traveling through transparent silica spheres and voids.

BLACK OPAL

Black Opal is Opal which shows a play of color within a black or dark body color when shown face up. Black Opals are the rarest and most valuable of all the opal varieties and command the most money. Their beauty is derived from their bright colors highlighted on a very dark background. A solid piece of opal with a natural black or dark background makes the stone appear darker on top. These are mined at Lightning Ridge and Mintabie in Australia.

Black opals come in all color variations and range from pitch black to gray giving the stone are darkish appearance when seen from the top. There are 7 shades of black in Lightning Ridge.

The "black" in black opal means the gemstone has a very dark body tone. A black opal can be crystal or opaque. The rarest color is Red, next is green and orange with blue as the most common color.

Is BLACK OPAL really BLACK? The answer is NO; Black opal has a natural black potch base or dark body color against which the play of color shows up brilliantly. This magnificent gemstone is the most valuable form of Opal. Ablaze with color, its dark appearance distinguishes it from white or light opal. Black opal is the family of opal which shows a play of color within or on a black (dark) body tone when viewed face up. Remember that the black in black opal means the gem has a very dark body tone, where body tone refers to the darkness remaining once you remove the play of color. The trade generally accepts black as those stones that have a very dark appearance if placed on a white background.

SEMI BLACK OPAL

Semi-black opal has an inherent darkness in its body color when viewed against a white background. Mid-gray stones are termed as semi-black.

The semi-black opal is found on most Opal fields, its background color ranges from gray to near black, one of its distinguishing characteristics is an almost smoky appearance.

Semi-black opals are from the same family as black opals, but they are not as dark.

LIGHT OPAL

Light Opal is opal which shows a” Play of Color” within a white, gray or light body color when shown face up. A solid Opal with a, usually, opaque light background. White Opals are usually the least expensive of all the solids. The variety is known as white opal and has a light background, and the colors displayed lean toward the pastel hues. Light Opals range in base color from white to yellow. If a light opal is translucent it is a semi crystal opal or crystal opal.

CRYSTAL OPAL

Crystal Opal is transparent or translucent opal where the colors are sharp and visible below the surface. A sold piece of opal without a natural black or dark back, the stone has a lighter, more delicate color on top. Crystal opals come in all color variations.

Crystal opal exhibits play of color, but, unlike white or black opal, it lets light pass through it. This type of opal has a degree of transparency which allows the colors below the surface to be visible.

Some believe them to be the most beautiful. Crystal opals can be either light or black crystal.

By crystal varieties definition, crystal opal is clear enough to read through against a light surface but it's colors spring to life when viewed on any dark surface, the more transparent the stone is, the more it is worth.

MATRIX OPAL

Matrix Opal is a fossil bearing porous Quartzite sandstone based opal from Andamooka in South Australia. When it comes out of the ground it is quite pale. It is darkened with a carbonization treatment to highlight the often vivid colors and resin treated during the lapidary process to protect the included fossils. The result is a beautiful gemstone with a satin finish that closely resembles black Opal.

An Andamooka matrix opal can be an affordable alternative to black Opal.

SKIN TO SKIN OPAL

Skin to Skin Opal is a term that is used to describe a piece of opal or a cut opal stone that is Precious Opal from top to bottom or, to put it another way all the way through.

All opal found has a skin on the outside. It is this skin that you can see when you are looking at opal in the rough and if you look at it from the top or bottom you normally cannot see anything but a rough surface. If the opal in between the skin(s) is solid opal or All Precious Opal, it is called Skin to Skin therefore a opal stone that is Skin to Skin will cost more than a Opal stone that is half Opal and half potch because there’s more precious Opal in the stone which cannot be seen in a photo of the stone. It will be mentioned in the write up and a photo taken of the back of the stone.

PLAY OF COLOR

Play-of-color (often referred to as “fire” in the United States) within the opal is the most difficult characteristic to judge for any opal and consists of the following factors.

Brightness: How bright is the overall play-of-color?
Spectral range: What range of colors is visible in the play-of-color?
Saturation: How pure and vivid are the colors forming the play-of-color?
Pattern: What are the size, shape, regularity and rarity of the play-of-color?
Consistency: Is the play-of-color, pattern, brightness consistent over the whole face of the opal stone?
Directionality: Is the play-of color visible from all directions as the opal is rotated?

Play of color is the way in which colors change as an opal is tilted, moved or rotated in different directions. Certain opals display different colors when viewed from different directions, or when the stone is turned, or when the light source is moved. This phenomenon, called the play of color, gives an opal stone color flashes, or schillers of different colors which vary from stone to stone. The play of color in Opals is truly exceptional and unsurpassed displaying sparkling prismatic colors which change and flash as you turn and move the stones body around.

FIRE OPAL

Fire opal is also fairly transparent (crystalline), but its background color may be yellow, orange, red or brown and it doesn't have the typical play of color (fire) of precious Opal. Fire opal with a red body color is also known as cherry opal. Mexico is the major source of this type Opal.

OPAL SHAPES

Opals are cut into a wide range of popular shapes. Oval is by far the most popular, followed by the circular or round, with teardrop, square, rectangle, and triangle also common shapes. Personally I prefer the freeform, then every stone cut is an individual and a one and only of it's kind.

Opals can also be a freeform from carving the opal stone, as some opals cannot be cut in the normal way as too much of the precious opal would be lost. Using carving tools all of the sandstone and impurities are ground away then the stone is polished. What’s left is what Mother Nature provided ~ a solid Opal Freeform.

OPAL DOUBLET

A opal doublet is created when a solid piece of opal is attached with epoxy to a piece of background material made to look black as a two piece composite This can give the doublet an appearance of black or semi-black opal on top. The opal and backing are stuck together with an epoxy to form a doublet, the stone being made of TWO pieces, hence the name DOUBLET.

The epoxy is impervious to water, acids and solvents, BUT neither triplets or doublets should ever be immersed or soaked in water, as it is still possible for the water to penetrate in between the two materials over time depending on what the cutter has used to make the two surface's black and what glue they have used, so play it safe and keep them out of the way of water.

Doublets come in all the color variations If you want to see if it’s a doublet ~ look for the glue line and straight edges between the precious opal and the backing.

OPAL TRIPLET

Opal Triplets are made up of a very paper thin slice of precious opal glued to a black base of glass or potch and covered with a protective clear quartz crystal cap glued on top (three sections). Commercial triplets come in all the color variations you can imagine.

OPAL FOSSILS

Opalized shells,crustaceans, sea creatures, snails, animal claws and bones, are some of the many objects that over time become opalized when buried in the unique environment of Australian clay and left undisturbed. That is what the general conception is, but in actual fact what happened was that over many thousands of years the buried shell etc, actually disintegrated and turned to dust or a fine powder and left a cavity, much like a jelly mold. As the opal silica jells seeped its way down through the sandstone it found and filled all the cracks and crevasses on the way down. This is how we have many types of Sea Shells, Pipes and Verticals which are the result of cracks and are always found in the Seam or level which use to be a seabed.

HOW ROUGH OPAL IS GRADED & SOLD

Rough opal parcels are sorted into a few grades: Tops, otherwise called 1st's, then 2nd's, 3rd's and so on. Color is the primary criteria for grading, but the buyer's also take into consideration the number of imperfections and faults, the size of the stones and whether a stone is the right shape to be cut into an oval or one of the other popular shapes.

Mine Run: Direct from the mine, the stones have not been cut or ground down. This means that there is more guess work in the cutting. Purchasing mine run opal can be risky.

Off Cuts: The miner has removed whatever opal he has a market for and sells what's left as off cuts. You can usually tell what you are going to be able to cut. You must still watch for cracks in the opal because once a crack becomes obvious, a stone can lose half its value.

Rubs: This can often be the best way of buying rough. The miner has cut and ground the stones into basic shapes, after having removed most of the rubbish. What’s left is a stone nearly ready for the doping and polishing process. This practice is mainly confined to opal from Lightning Ridge.

Opal is officially sold in troy oz. there are 30.103 grams to a troy oz and approximately 30 oz to a kilo.

LOOKING AFTER YOUR OPAL

Taking Care for your Opal: Never apply oil of any kind to any opal, oil will not soak into a solid opal and does no good! Oil can have additives that can possibly pit the surface and certainly will make a highly polished stone look dull.
Extreme heat and cold are opal killers. Sudden temperature changes can cause a solid opal to crack or craze.
Water, a solid opal may be kept in a small container of water for extended storage to protect it from sudden temperature changes. The water will not affect the opal stone. Never soak doublets or triplets in water. Water soaking can effect the glue etc, attaching the crystal cap or bottom section.

You can clean the opal stone itself with a soft cloth and Menthylated Spirits (alcohol). Just put a little on a cloth and give the opal a soft rub, this will clean the stone and also take any oil that has gotten onto the stone, remember even your fingers have oil on them.

Opal Jewelry: A mild soapy luke warm water solution and a very soft brush may be used for jewelry set with solid opals, making sure that you rinse off the piece with clean water after cleaning. The safest cleaning method is to use a damp cloth followed by jewelers polishing cloth for the metal.