Over the past several months, due to various enhancements amongst various colored stones, the demand for untreated or unenhanced stones has increased. If a stone is in fact unenhanced, there can be no question as to what treatment has or hasn’t been applied to it. However, pending on what type of gem we’re talking about, these are more or less common-and priced accordingly.

I came across some piece of information that said if you wish to tell if an aquamarine is heated or not, a gemologist with a standard loupe can tell. If you’re very lucky, and/or you’re looking at a rough specimen, that may be one thing. The only stones that I’ve seen that have been said to have been unheated looked more like green beryl than they did aquamarine. In case you’re wondering, green beryl is the same chemical composition as an emerald, except they are much cleaner and significantly less saturated in color. A lot of times, aquamarine rough comes out of the ground in a unique shade of green.

Well, do you want a green aquamarine or do you want a blue aquamarine? The overwhelming majority of buyers want blue, and not green. So if it’s blue it’s heated. Is it?

Consider the following 2 images:

Based on looking at the picture, can you tell which stone is heated and which one isn’t? They’re both of a medium blue though they might appear to be a dark blue in the imagery. The top specimen is an elongated cushion cut specimen believed to be from Brazil weighing over 6 carats. The second image is of an unknown carat weight originating from Afghanistan and does not show evidence of a thermal enhancement to the rough. The previous illustrations are around 20x or less.

How can that be and how can you tell? The reality is that if you saw either in person, you would swear both were heated. The second specimen shows evidence of heating from natural geologically occurring events. The first image is another story.

Usually in the case of aquamarines, material from Brazil or some other locality is a distinct green color. They have a high amount of iron in them. However, the heating process causes an electron transfer within the iron ions, and thus changing the color from green to that nice blue. This is a permanent treatment.

There is a problem though with heating an aquamarine to get that lovely coveted color. You have to make sure that when you place the rough in a kiln, it has to be relatively free of inclusions-at least those that are eye visible. If not, the heat will cause enough stress for the rough to break. So a given piece of rough might have to be cut into smaller parts in order to safely heat treat the stone.

There are some tell tale signs that you can look for in an aquamarine that says mother nature did it’s own heat treatment. It’s all in the artifacts. The only problem is, you can’t always see them with a 10x loupe or even a standard 30x microscope.

1. When the piece of rough was obtained to cut the second specimen, there was a polished window in which you could see a visible white silk. The arrangement of this fine silk was such that you could see it intersect in portions at 60 degree angles. This is consistent with the hexagonal shape off beryl crystals.
2. Look for in tact crystals within the specimen that have perfect terminal ends. Heated stones will have very rounded and globular type crystal inclusions in them.
3. Look for an iron grain. You can see a distinct grain within the unheated specimen that you can’t see or anything like it in the heat treated version.

These are some of the artifacts I’ve observed when looking at both specimens. The lapidary who cut the second specimen also made some interesting observations and erroneously said it had to be topaz. Then again, given the nature of the specimen and how it was cut, there are logical explanations that could lead one to believe that, but at the same time overlooking some obvious signs in the rough would have given someone a clue.

Let’s take a closer look at the first specimen.

1. The center artifact (left) illustrates a misshapen crystal. When you heat the specimen, these things decompose and appear more rounded.
2. There are elongated inclusions near the right that are distorted. There is clear evidence of decomposition of these artifacts. This happens during a fast heating process which is standard with all stones in which heat treatment is applied.

In this image, we can clearly see small sphere like inclusions. These are more or less perfectly round. This is a good indicator of heat treatment being applied. You don’t see these perfect spheres in unheated stones. This particular image was taken somewhere near 60x.

The images obtained for that stone weren’t for an in depth study, and there was little evidence of any additional artifacts that could be explored and kept in focus. Keep in mine that aquamarine is a GIA type I gemstone. In other words, stones can be completely eye clean or better for the most part. With one exception that you had to catch perfectly with the loupe, there was one rounded globular single phase solid inclusion with evidence of iron. That was it. The best inclusions that could be found in this specimen are as minute as they are at 60 magnifications.

It is quite possible to see an aquamarine that appears to be flawless under a loupe, and you won’t see any of these artifacts. With 20 or 30 magnifications, you may see nothing beyond some very small dots. That’s it. Obviously, this imagery goes beyond that.

Now, let’s look at some imagery of our unheated specimen.

This is at about 20 magnifications with ambient light present. There are some very minor spherical type inclusions noted, but nothing really significant. They appear as such at least from this level of magnification.

When viewed at 22x under a darkroom condition, we can clearly see a significant higher amount of silver tone. The cutting may have something to do with that in comparison to the other specimen in which darkroom photography couldn’t be obtained at the time. However, you can readily begin to see some patches of iron about the stone. You won’t see that with a heated aquamarine.

We can see these iron stains much better and we can begin to see a very laminar and fine grain at 45x. Note in the previous illustration how there was no such pattern at even 60x.

This is at 45x. We can see the tell tall terminal ended crystal. When we observe within the same area at 55x at another viewing angle, we can observe the same thing.

At this level of magnification, the visibility of the grain is more pronounced. In heated stones, these undertones and grains tend to react and more or less blend in with the rest of the body and diffuse throughout the crystal matrix. This is obviously not the case. The circled artifact is what is believed to be part of an iron rich terminating ended crystal in tact. Had heat treatment been applied after the rough was mined, this artifact would have been destroyed.

This is how the grain of this specimen looks at 205x. If you notice, there are several smaller crystal inclusions. While they appear to be partially decomposed, they show irregularities that could only be attributable to growth after a thermal event. It is possible that these crystals were introduced into the matrix through a natural and metamorphic event. Though not documented or evident as shown, there were some flower patterns of iron noted at high levels of magnification above 200x under the microscope.

When this piece of rough was cut, you could clearly see that there were conchoidal fractures in the uncut specimen. However, the lapidary who cut the rough said it had a perfect cleavage to it.

If you notice, the table of the stone is parallel to the grain. This is how emerald cuts were termed as you could get a cleaner cut stone by cutting in a like manner. As a result, you could cleave a perfect plane by cutting with the grain just as one might as if they were cutting a piece of wood.

Consider the image below:

This was obtained near the culet of the stone. Pending on how you view the monitor, you can see that there are what appear to be conchoidal fractures within the specimen. This was obtained at 172x. This type of cleavage is consistent with aquamarine as well as many other stones, but not topaz.

So which is better? There is absolutely nothing wrong with a heat treated stone. Most of what is out there is heated to give the beauty we see with aquamarines that many of us cherish. However, when mother nature heats things naturally to achieve a like result, this is something that is quite uncommon and makes that particular stone just a little more special and rare.

-joe