It has become common practice for both private individuals and dealers to speak of inclusions when the stone, in addition to being 100% transparent, still contains small minerals, cracks or fluids that can be seen with the eye. These are not always to be seen only negatively.
Lying in the right place, they cannot detract from the color of the stone. On the other hand, they are witnesses to the formation of the stone, confirm it as naturally occurring and can often also provide information about the history of its formation or the country of origin (e.g. in the case of rubies and sapphires).
As an investment, this is an important factor, because if a stone can simply be found to be natural with a magnifying glass by its inclusions, the technically experienced prospect has an opportunity to make an offer to buy directly.
In post-war history, it was shown that, especially in barter transactions (food for stone), smaller stones with inclusions were more likely to be traded than stones without inclusions, which the barter could interpret as “glass”.
In the case of larger stones (investment), however, the presence of the smallest inclusions is not negative, since it is also “simpler” to determine the naturalness, even if it is not exchanged for food, but has to act as a security deposit or similar.
Recognized laboratories around the world now use inclusions as a first indication in their investigations; if none were present, only a chemical analysis would primarily help.