Opal is the fourth Precious Gemstone!
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Australian Matrix Opal cuff bracelet
Opal is a soft, multicolored gemstone. Opal is hydrated silica - it has a very high water content. The opal pendant on the left (below) holds an Ethiopian Welo opal; this type of stone displays broad flashes of color (photos can't show this accurately). This opal is considered a precious gemstone. (In rare cases up to 20% of the weight can be water!)
Opal has been used for thousands of years to create beautiful carvings, beads and cabochons.
Opal is found in the western United States, Australia, Ethiopia, central Europe, Peru and Mexico.
Opal is generally found in two varieties. One type, called "common opal", is a translucent gemstone that displays no (or very little) fire. Mexican fire opal, despite its name, is an example of common opal. It ranges in color from white to a gorgeous intense red. The ring at right was made with this kind of Mexican opal. Mexican fire opal is the one type of opal that is also commonly cut into faceted stones.
Other Common Opals are pink opal and blue opal from Peru. They display no fire, but they're popular stones.
Precious opal has a base color that can range from white to black. Darker background color stones usually cost more.
This type of opal displays multicolored "fire". This is caused by white light moving through the microscopic silica spheres that the opal is composed of and breaking into component colors, similar to a prism. These tiny silica spheres are arranged in perfect grid fashion. The grids are stacked on top of each other. When the light moves through the perfectly ordered, stacked silica spheres the opal shows bright flashes of red, green, blue and other colors, depending on the way the spheres are oriented, their size etc.
Common Opal is also made up of the same silica spheres. But they're arranged in random fashion, like balls just tossed into a box. The silica spheres must be perfectly lined up and stacked in an orderly way for opal to show play of color.
Opal recovered from seams in rock can be cut into solid cabochons. Most Lightning Ridge and Coober Pedy opal is this type. Many opals are different, though ...
"Matrix Opal" is a soft material that needs to be processed (cooked with an acid / sugar solution) to darken the matrix rock, then it stabilized with epoxy. Once done it is beautiful opal. The cuff bracelet above is set with matrix opal.
Boulder opal is similar to the natural opal doublets described below; but its usually a thicker piece of opal. The pendant on the right side holds a pretty blue Australian boulder opal.
Koroit boulder opal has small veins of brightly colored opal running through the stone. Yowah Nut opal is similar in appearance, with beautiful random opal patterns in host rock.
Opal cabochons can be solid, or they can be doublets or triplets.
Opal doublets are composed of a layer of precious opal bonded to a base with epoxy - usually dark colored potch or common opal, usually opaque with no fire. The top is then finished and polished like a solid opal cabochon.
Opal doublets can also be natural. The cutter gets close to the natural stone holding the opal, but a thin layer of precious opal is left. The stone back is flattened, and the precious opal on the front is polished. It isn't solid opal; technically, this is a doublet, although natural. The ring on the left contains a natural Lightning Ridge opal doublet.
Opal triplets are made in a similar manner, with opal bonded to a potch base. However, the opal can be a very thin slice, because it is covered with a cap to produce an opal "sandwich". The cap is usually clear crystal quartz but can be acrylic (plastic).
An inexpensive alternative is the mosaic triplet. Instead of one large but thin slice of opal, many small pieces are tightly fitted together in a "mosaic" on the base, and then capped.
Synthetic opal is available. Named for its creator, Pierre Gilson Sr., Gilson® synthetic opal is a true opal. It has the same chemical composition and properties when compared to natural opal, with a few differences. It looks different under a microscope because it forms under controlled conditions, as opposed to natural opal. It has a lower water content. This makes it harder than natural opal, at an 8 on the Mohs hardness scale. It withstands very high heat. It compares visually with the finest Lightning Ridge black or Coober Pedy crystal opals. Chatham also makes a synthetic opal.
A lot of the "opal" - especially inlay opal jewelry - sold today contains imitation opal. It may even contain bits of crushed opal, but it is made of resin - an epoxy (glue). Modern imitation or simulated opal looks very good; sometimes uninformed sellers call it synthetic. Opal with a resin base is not synthetic; it is simulated. This is fine; there is nothing wrong with simulated opal but it should be disclosed; the customer should be told what they are buying. Ask if you are not sure.
Opal has been traditionally
believed by some to enhance the emotions of the wearer, making it easier for
get in touch with their inner feelings.
Opal Care Tips
The best way to clean an opal is to soak it in clean, clear water, then dry it with a soft cloth.
Natural opal is a very soft stone which should not be cleaned with commercial jewelry cleaning compounds.
Opal is a porous stone which can absorb liquids that can affect its color and erode or even dissolve the stone.
It should not be worn while washing dishes or using harsh household cleaning chemicals.
Ultrasonic, chemical or steam cleaning of opals is not recommended - ever.
A rouge polishing cloth is okay but a clean, soft cloth is best.
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