Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

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AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...
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How to Identify Aquamarine-Filled with Colored Polymer Type of Treatment: Impregnated

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This article introduces a simple and non-destructive method to identify impregnated treatments in aquamarine.

Polymer-filled aquamarine examined for treatment


Basically, what happens is that fractures in the aquamarine are filled with a polymer mixed with dyeing material. This not only enhances the color of the aquamarine but also hides the fractures.

The result is a beautiful, polymer-filled aquamarine that is often sold under the name of Santa Maria Aquamarine. Most of these treated aquamarines come from China (in bead shapes, making bracelets or other jewelers items) and Thailand (in faceted and cabochon shapes).

Gemstone traders purchase them at wholesale prices and then sell them at retail prices on social media platforms, eBay, or other e-commerce networks.

To identify a specific type of treatment in aquamarine, here's what you need to do: Grab the stone with a stone tweezer or simply use your fingers. Then, position a source of white light (fluorescent light / LED light preferable) behind the stone, just like you can see in the pictures that come with this guide.


Grab the stone with a stone tweezer or simply use your fingers. Then, position a source of white light (fluorescent light / LED light preferable) behind the stone.

 

Aquamarine held against white light for treatment examination
Grab the stone with a stone tweezer or simply use your fingers. Then, position a source of white light (fluorescent light / LED light preferable) behind the stone.

Now, pay close attention to the stone and look out for any blue flashes or a cloudy appearance. You can see an example of this in the picture below.

Bluish flashes in polymer-filled aquamarine
Note the strong bluish fleshes

If you want to dig deeper and get more detailed observations, you can use a 10x loupe or a gemological microscope. Take a closer look at the color concentration within cracks and fractures, and who knows, you might even spot some air bubbles.

Blue colour concentrated in fractures of treated aquamarine
Note the blue color concentration in cracks

By following these steps, you'll be able to identify the treatment that has been done on your aquamarine. So go ahead and give it a try!

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