Opal Gemstone Guide - October's Birthstone

General Opal Information

There really is something magical about opals with their color flashes and color play. The term "Opal" comes from ancient greek and latin words meaning color change and boy do they. Almost all opals come from Australia which is why they are their national gemstone but there are a few pockets in other areas.

Opals are a form of silica which grows in the crevices and cracks of rocks where water flows. The presence of silica creates the color play you see in opals and it can very from flashes in reds, blue, yellows and oranges or there can be color flows that look like ribbons flowing through the stone. Here are an example of each...don't they remind you of the Northern Lights?


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In the example on the left you can see the flecks of color that almost sparkle while in the example on the right you can see the color literally flowing through the stone like liquid.

Opal Colors

There are three main types of opal color classification, the first and most commonly recognized are the white opals. White opals are any opal that has a majority white or cream base. Below are a few examples of white opals.


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Next, are the far less common and far more valuable Black Opals. These opals are any opal that has any base color other that white or cream, so black opals can really have a blue, green or black base. These opals are very rare and hence much more expensive. Here are two gorgeous black opals.


Finally, we have the Fire Opal (sometimes referred to as Mexican Opal), is very unique because it is actually translucent and comes in bright versions of red and orange. While it is an opal and even it's translucency has a thickness, these opals look nothing like the above mentioned. Since they are translucent they are cut in a faceted cut instead of a cabochon. These opals are not as rare as black opals but they are very popular leaving them at a similar price point.

 Opal Cuts

As mentioned above fire opals are cut in traditional faceted cuts because of their translucency. White Opals and Black Opals are almost always cut in cabochon, square or seed cut. A cabochon has a rounded smooth top with a flat bottom. This type of cut gives an opal the most color play and the higher the dome the more color play it will have. Seed cuts are spherical like a pearl and square cuts are chunks with 90 degree angles.


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In the above examples the ring on the left is made up of teardrop cabochon white opals and seed pearl opals.

What to Know Before and After Buying Opals

 All opals are porous softer stones, that have one of the lower hardness rankings of all gemstones. They also have a high water content. So it is very important to never buy an opal that has any type of chip or fracture even if it is only visible from the bottom of the stone because once an opal fractures it will continue to fracture.

To this end you should always check the bottom side of an opal before buying it. And it should always be visible in the ring setting. Do not buy an opal in a closed bottom setting because water can get trapped there and ruin the opal and you can not see if there are any chips or cracks. Also, if you look at the underside of an opal and it looks like black paint it is doublet or triplet which are thin slivers of opal stone layered on top of each other and are much less valuable.

As for caring for your opal, opals can last a lifetime but they do require a little more care. If you are playing tennis or going rock climbing do not wear them. Since opals are porous they can absorb water and if they absorb too much it can cause them to fracture, so never wear them in the shower or while doing dishes. And never ever soak an opal to clean it.

Opals (of all variety) are the birthstone for October and the anniversary stone for the 15th wedding anniversary. There are synthetic versions of opals but they can easily be spotted because they look like glue with confetti. We have all types of opals and you can see them all here Scotch Street Vintage Opal Collection. And as always if you have any questions we are always happy to help you can contact us here.


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