Opals are our favorite stones here at Earth Art! They are also the most misunderstood of all gemstones and so they get their very own section. In this article, I am going to do my best to outline everything from proper care for an opal, to the various origins, types, value and more concerning opals. I am going to break this down into the Region that each opal comes from.
Crazing: These are tiny micro cracks that form on an opal if it dries out too much. Not all opals do this, but sometimes they do after many years of neglect. Generally if an opal sits in a display case for several years and does not crack or haze, it is not likely to any time soon. Hazing will also sometimes make an opal look cloudy or milky. Hazing is most common in Mexican Opals and Virgin Valley Opals
Cracks: This usually happens if an opal gets saturated in water, and then dries out too quickly. it can also happen after a sharp impact with another hard object.
Color change: If an opal is soaked in a liquid that has a lot of chemicals in it, the opal can absorb some of the chemicals, right along with the water. For this reason, we recommend that you do not wear opal jewelry in the ocean, hot tubs, or while washing dishes, or any other activity that would risk prolonged exposure to impurities in the water. This is especially true for Ethiopian Opals, and less of a concern for Australian opals.
Aussie Opals are the best opals money can buy. While there are several other opal varieties which can have better fire, they all fall short in one way or another when it comes to durability.
Australian opals have stood the test of time. I have come across opals over 100 years old that still are fracture free, and full of fire. With proper care, most Australian opals will last for generations. Australian opals are the only opal that is a true black opal. They also display a very wide range of fire patters and background colors including clear, white and grey. Australian opals are less likely to be treated. The most common "treatment" is for them to made into doublets or triplets, which are easily identified without any testing equipment.
A good Australian opal will fetch a much higher price than its equivalent Ethiopian opal. Because Ethiopian opals have flooded the market as of recent, many Australian opal mines are forced to raise prices to make money from the limited number of opals that the mines produce. An equivalent Ethiopian opal will often sell for a tenth of the price of an Australian opal of the same size, and fire.
There are many grades of Australian opals, unfortunately, the grade that most consumers are familiar with, and associate with opal, is what is called "Commercial grade". Commercial grade opals are white background stones, with a tiny amount of pin-prick fire that barley even shows up. Blagh. We don't deal in these kinds of opals. They are commonly used in larger jewelry store chains simply because they are cheap and easy to replace or order in specific sizes. Their pretty much worthless, so don't buy them.
Medium grade opals will have good color play and can have any range of light to dark backgrounds. Depending on how bright the colors are, and how concentrated the background it, the price can vary from $25 to $100 per carat.
High end opals are usually opals with black backgrounds and very bright and vivid color play that plays across the full range of the stone. These stones are very rare and will often pull in prices from $150 to $300 per carat.
Collection Grade or Gem Grade opal is so rare, that most people will never see one in person in their life time. These will fetch very high prices. The stones also usually display a particular pattern in the fire such as a cobblestone or scale like pattern which increases their value.
Most of the opal we deal in is in the mid-to high range price bracket.
Care: Try not to let these opals spend a lot of time in water (Don't soak your opals in water or oil). But also don't let them sit in a dry safety deposit box for 20years. Opals like to be worn. So try to wear them at least once a year if it is a very special piece. Or everyday if it is suitable! Just from being exposed to the natural oils in your skin, and the natural humidity in the air it will obtain all the moisture it needs.
Such a seductive stone! Most Ethiopian Opals are some what transparent in appearance, which allows more layers of fire to appear in the stone. This in turn makes them look full if life and fire!
Ethiopian opals form in little nodules. They are mined from the sides of cliffs in Ethiopian, Africa. This differs from Australian opals since the mining is much easier and the opals do not form in seams. For this reason, finding opals that are deeper in volume is much more common. The color play in the opal usually swims throughout the full stone rather than appearing in layers. The nodules are usually broken open with hammers to tell if there is any good opal inside. This is one reason which rough Ethiopian opal is always seen on angular jagged chucks, often with lots of fractures. A cutter then needs to cut away all of the cracks to achieve a stone that is free from chips or fractures. While cutting each nodule with a saw would yield more clean opals, it would take a lot longer, so since the opal is so plentiful, it is easier (and cheaper) to just smack them with hammers and pull out the good pieces.
At the moment, Ethiopian opals are flooding the market with very nice, yet surprisingly affordable stones. You can get a very nice stone for well under $100 per carat.
Probably the least expensive opals currently on the market. These stones have a great range of fire to them, and they also expand the range of opal colors and include clear, white, grey, cream, orange, yellow and brown. They are available in calibrated sizes with makes them easy to buy for ready made ring settings and even larger stones can be found at reasonable prices.
95% of Ethiopian opals are hydrophane opals. This means that they absorb water very readily. The more water they absorb, the more clear they become. Their fire also seems to disappear as they take on water. Then, as they dry out, the fire returns and the opal will return to its normal milky body tone. The transition is actually so quick, that you can place an opal on your finger, and run it under a stream of water, and within moments, you'll note that the outer edges of the stone have started to turn transparent. Place the opal in a cup of water and it will take about 3-5 minutes for a 1 carat stone to turn completely transparent. Then place the opal on a paper towel, and a few hours later you'll see that the body tone has returned to the opal. While this is an interesting experiment, I don't actually recommend trying it. This places a lot of stress on the stone, and if it dries too quickly, the opal can crack of craze. If you do soak an opal, the best way to allow it to dry is as slowly as possible. My strategy is to place it on a wet towel. Since the towel will take all day to dry if indoors, the opal too will also take at least as long since it is in contact with the towel. This reduces the internal stress on the opal.
How to tell if you opal is hydrophane? Easy: Lick or moisten your fingertip before picking up the stone (or just lick the stone). If it is hydrophane, you'll feel it sticking to your finger or tongue as it tries to absorb your moisture.
Since there are so many Ethiopian Opals on the market, there is not much use for the lower grade opals. These are often sold in large lots for a few bucks per carat.
Mid grade stones will tend to have the fire equal to that of a high end Australian opals, but will cost much less.
A high end stone is usually only slightly better. The fire may be more saturated and consistent. The price for these stones may be as much as doubly that of a mid range stone.
Chocolate opals are a form of Ethiopian opals. They are typically brown or red. The best stones are bright red with good blue, green and purple fire in them. Finding a chocolate opal that is intact will often mean breaking opal hundreds of opal geodes.
Honeycomb Opal: This refers to a particularly rare pattern that seems to occur in Ethiopian opals ever so often. The best way to describe it is that it is like a honeycomb shaped web of more opaque opal that seems to float within the main opal. The fire within the opal then seems to peak out between all of the spaces. This is very rare and a good stone will be worth several times that of a stone without the pattern.
But first: Time for a talk about opal terminology.
The term "opal" is simply a name for any stone, which has a certain anatomic make up, which makes it an opal. Not all opals have moving colors in the stone.
Matrix refers to the stone surrounding the opal which is not opal, this can be sandstone, ironstone, or even just dried mud.
Matrix Opal is opal whish has sort of permeated a porous matrix, like sandstone. So what you see is the matrix, with tiny flashes of color in the stone. Opal like this can be found in Canada, Louisiana, and Honduras, to name a few.
Precious Opal is an opal which has color play.
Non-precious opal does not display colors shifts or color play. I'll give some examples of this soon.
Color Play refers to the movement and/or shift of colors within a stone as the stone is turned in the hand. Strong color play can mean the stone has more colors and a better color shift. Sometimes, the color play is referred to as the "Fire" in an opal. this is still more or less correct, but should not be confused with "Fire Opal"
Generally when the average person is talking about a fire opal, they are thinking of an opal which has "color-play" within the stone. In actual fact, a Fire Opal, refers to a red, orange, or yellow opal from Mexico, so named for their fire like colors. Mexican Fire Opals are considered a Semi-Precious Gemstone, but are not "Precious Opal.
Confused yet? It gets better!
So back to Mexican opals:
These opals most commonly do not display any color play in the stone, but rare stones can be found which are both fire opal and also which display color play! These are true beauties! The correct term for these would be Precious Fire Opal.
Mexican opals are generally mined from a light brown or beige matrix. Sometimes they are carved so that the opal is cased in the matrix as part of the finished stone. These tend to look sort of like eyes. These are much less valuable, but can be very beautiful.
Fire Opals are traditionaly faceted stones, but they are also found in cabochon form as well. The more red the stone, the better. The thing that makes Mexican opals so rare is that they are prone to drying out and cracking within a year after they are mined. thus, old stock, that has sat forat least a few years, and is still in good shape, is usually a good bet.
Value: A top notch red mexican fire opal, with color play can fetch a very high price. These are usually cut en cabochon to preserve as much of the stone as possible, but faceted stones can be found as well.