Assertion: specific impurity | /r/HasProperty | e.g. beryllium
Facets:
Source sentences:
text: In contrast, however, heat treatment combined with the deliberate addition of certain specific impurities (e.g. beryllium, titanium, iron, chromium or nickel, which are absorbed into the crystal structure of the sapphire) is also commonly performed, and this process can be known as "diffusion" in the gem trade.