April 10, 2014



The concept of inclusion can be defined as follows:


  • Inclusions are small-sized minerals located inside a larger-sized crystal (host crystal).
  • Cavities that appear in the mineral, filled with liquid and/or gas.
  • Such inclusions are characteristic of the hosting crystal and they are a sure way to differentiate natural gems from synthetic ones 



When I examine a gem, I always follow the same steps:


First I classify the gem’s colour, measurement and weight, then I look at the refractive index, the spectrum, if it does or doesn't have pleochroism or fluorescence, if there are doubts regarding specific gravity and, finally, I study the gem under the microscope. This is for me, the most fun part of the whole process.


Solid inclusion in tourmaline

Inclusions in synthetic ruby


As I already told you before, a synthetic gem is a gem with the same physical characteristics as a natural one, but is man-made. So, until the final stage, in most of cases, we will get the same data as if it were natural. It is here when inclusions become more important.


In general, the appearance of inclusions is normal. If there are many, the stone loses brightness and beauty. Inclusions are decisive in classifying the quality and value of the gem.


If there are inclusions that don´t affect the beauty of the stone, they bestow the gems with an added value. There are some inclusions that are exclusive to certain gems, so it is not necessary to perform further tests.


Lily pads in Peridot

Inclusions in synthetic yellow shappire


On the other hand, there are inclusions that will only be seen in synthetic gems, for example curve growing lines. These can even provide information about the type of synthesis, or if we see the typical  “chevrons” then we know it is hydrothermal, or the twisted veilstypical of the flux synthetic gems. 


Depending on the inclusion, you can even determine the gem’s origin.


In other cases you can see the inclusions are 'deformed', you can see the gem has natural but strange inclusions  that look synthetic; this is a clear example of when the stone has been treated ( I call it 'mistreated'), as, if it had been properly treated, deformed inclusions should not be visible. In other cases, what we can see is that where two-phase inclusions should appear, there are dry, frosty looking inclusions, so you 'suspect' that they have undergone a thermal treatment.


And, in the worst-case scenario, you can find a completely clean stone, so clean in fact that even when you magnifying it 50 times you see nothing. In these cases I always feel uneasy, as Nature is imperfect. What happens in these cases? Can you say if it is natural or synthetic? I wouldn´t say anything without performing more and more expensive tests.


I haven´t yet met a gemologist or geologist who doesn´t find exclusions beautiful. And, as a piece of advice:  an inclusion is a guarantee of designation of origin, whatever origin this is.

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