Very interesting and enriching the article published on the GIA website link https://www.gia.edu/blue-diamonds-have-surprise-origin-and-link-to-ocean
Scientists have concluded by examining the inclusions, that is, small pieces of minerals trapped in the diamond during its crystallization, that the blue “type IIb” diamond was formed at depths of 410 to 660 km, four times more than the other types of diamonds that are formed 150-200 km deep. Prior to this study of 46 “type IIb” diamonds in GIA, no other mineral inclusions had been identified in this type of diamond.
Comment:
The blue “type IIb” diamond contains boron, a chemical element that is an electric conductor. However, a Brazilian natural blue diamond of unknown origin has recently been examined, which did not show electrical conductivity, probably because it was not “type IIb”. The blue color in diamond can be caused by several factors. According to the article published in Gems & Gemology, Summer 2018, Vol. 54, No. 2, although blue color is often associated with boron impurities, the color of diamonds in this range (including gray and violet) also originates from simple structural defects produced by radiation exposure or from more complex defects involving hydrogen.