Minerals and gemstones are formed in nature and usually this does not happen without a degree of natural violence. In addition, the creation of a gemstone is often a lengthy process that will rarely go undisturbed. It is therefore not surprising that all kinds of “pollution” can arise during this process. This “contamination” is often referred to as an inclusion or imperfection. Inclusions can be, for example, pieces of plants, insects, other minerals or even liquid.
Often these inclusions are so small that they are only visible with a microscope or under magnification with a loupe. However, sometimes they are larger and can be seen with the eye (without magnification).
A good example is this photo of an emerald with a very clear inclusion.
For gemstones, it is often the case that the purer a gemstone is, the higher its value. However, inclusions that do not affect the brilliance and fire of the gem have no or limited effect on the value of the gem.
Some inclusions can even increase the value of a gemstone, such as the inclusions responsible for the cat's eye effect or the stars of star rubies, for example.
A gemstone that regularly has a beautiful cat's eye effect is Opal.
In addition, there are collectors who look for nice inclusions in stones because they make the gemstone more interesting.
An interesting example is this Quartz with Petroleum inclusions.
Adamast uses the classification below to indicate the clarity of the gemstones.
Gems without inclusions
Gems where (possible) inclusions cannot be seen with the naked eye.
Very Slight Inclusions
Small inclusions that are visible to the trained eye or when viewed under 10 x magnification.
Inclusions that can be seen with the naked eye.
Clear inclusions that can be seen with the naked eye.
Gems which allow light to pass through without diffusing (scattering) it.
Gems which allow light to pass through with diffusing (scattering) it.
Gems which do not allow light to pass through.