Raw Opals: 5 Essential Identification Techniques

Opals are gemstones that consist of silica and water and are made over a process that lasts millions of years. Of the many precious gemstones in existence, opal is arguably the one with the most spiritual significance, especially in religions that emphasize the importance of meditation.

Whatever your reason for wanting an opal, you must be able to distinguish the real stone from whatever fakes you might encounter in the wild.

Methods Of Identifying Raw Opal

Raw opal
Ethiopian Raw Opal
Image credit: VIKAS GEMS

Being able to know if an opal is real or not is very important for anyone that intends to buy one or that has gotten one.

Opals are unique because their value is not determined by the clarity, cut, or carat like most gemstones; while these play a role, an opal’s value is mainly determined by its color. Because color is a huge determinant of an opal’s value, it is very easy to make a “little” mistake that ends up costing dollars if you don’t know how to identify a real one.

Explained below are some of the ways you can identify a raw opal.

1. Professional Testing

The most reliable way to ensure that a stone is a raw opal is to take it to the professionals to check it out for you. You can do this by either taking it to a reputable jeweler around you or an independent agency like the Gemological Institute of America (GIA). You should take your stone to the GIA for testing because most jewelers would eventually take the stone to them for testing anyway.

The advantage of testing your stone professionally is that they are more experienced and have better equipment to conduct these tests. Because of the advantage that they have over the layman, they would not make the mistakes that you might.

Also, nowadays there are artificial opals so well done that you would not be able to tell the difference. A professional check would let you know if the opal you have is a natural or artificial one. 

Usually, the GIA evaluate a stone and grade it; however, they do not grade opal stones. When all tests are complete, all the information about your stone would be put together into a unique and comprehensive certificate.

2. Test Its Density

This method would involve you doing some calculations to find the density of the stone that you have. The density of raw opal is 2.09g/cm3, so measuring the stone to check its density is another great way to confirm if what you have is raw opal. 

To perform this test accurately, you would need the following materials:

  • A scale that reads in grams, preferably an electronic scale.
  • A container of water that can measure milliliters.

Step 1– Place your stone on the scale and record its weight.
Step 2– Record the starting quantity of water in your container.
Step 3– Place the stone into the container carefully to avoid spills, wait for the water to settle, and record the new quantity in milliliters.
Step 4– Subtract the previous quantity of water from what you have after.
Step 5– Divide the weight of the jewelry by the number you got above, and the answer you get is the density of the material.

The formula in simple terms = Weight / (Water quantity after – Water quantity before)

While it might be possible to fake the appearance of an opal, trying to get an exact density value is not as easy. However, other materials might have a similar density as raw opal, so this test shouldn’t be a standalone test.

3. Pattern Observation

identify raw opal
Ethiopian Raw Opal
Image credit: VIKAS GEMS

One of the ways you can know things that are naturally formed is that multiple samples would not look perfectly identical and that is the case with the colored patterns on an opal. These colors are a result of the unique process known as light diffraction that happens when you shine a light on an opal.

Light passes through the spheres and gaps on opal and splits, the white light gets split into different colors on the spectrum which bounce out of the stone to beautiful effect.

This process of diffraction can be synthetically achieved too to create stones that look like an opal but aren’t. The key difference is that these manmade stones are mostly uniform, and an overwhelming majority of natural opals you find are more random in appearance. 

You can observe the patterns on an opal with your naked eye to see if they are too identical. On some fake stones, you might need to use a magnifying glass such as a loupe to carefully examine the stones for extreme uniformity.

4. Check If It’s A Doublet Or Triplet

The value of opals is mostly determined by their color and this makes transparent opals worth little or nothing in the market. Doublets are created to make the transparent opals have that beautiful look of a bright one. 

Doublets are made by attaching a black common opal (called potch) to the back of the opal; this makes the colors of the opal stand out as a solid one would. A doublet might look like a solid opal to the unsuspecting but its value is much less than it.

To check if the stone you have is a doublet, use a loupe to carefully inspect the place where the opal is joined to the potch. On most doublets, the meeting point between the opal and potch is a straight line which isn’t the case in natural black opals. Also, when you place a very bright flashlight in front of the opal and look at it through a loupe, you’ll see the imperfections in the gum, such as air bubbles.

Opal triplets are similar to doublets but involve placing a thin sheet of opal between a potch at the back and quartz on top to make it look like a solid opal. The methods explained above to use in detecting a doublet can also be used to identify a triplet.

5. Check The Setting

In jewelry creation, valuable stones are usually set on valuable metals, driving up the overall value of the jewelry. If there’s a stone set on a piece of jewelry and you do not know if it’s an opal, you should first try to confirm what kind of material the stone is set on. If the stone is set on a cheap metal like iron or stainless steel, it is most likely not an opal stone.

Opal would usually be set on silver or gold, and it’s easy to know if the base metal is gold. Gold materials usually have a hallmark inscribed on a hidden part of the jewelry, and you might need to use a magnifying glass to locate and read the hallmark. This hallmark usually indicates the carat size of gold, the producer, country of origin, or other information.


As with many precious stones, there are different ways to check the authenticity of opal and prevent yourself from falling for lookalikes. Personally try out the methods explained above to ensure you do not buy the wrong thing; however, the most reliable way of confirming your stone is opal is to give it to the professionals to handle it for you.

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