John Pollard, Senior Director of Education for IGI, discusses unique inclusions in both CVD and HPHT grown diamonds.
John Pollard Senior Director of Education for IGI
IGI's Senior Director of Education recently wrote a detailed anaylsis of inclusions that are unique to CVD and HPHT grown diamonds and the insights are fascinating.
Key takeaways from this analysis:
Inclusions seen in HPHT-grown diamonds
In the HPHT process, a metallic catalyst is used to dissolve the carbon which migrates to the diamond seed, stimulating the growth process. Logically, pieces of that metal catalyst, which do not melt entirely, can become trapped within the diamond crystal.
Metallic Features
Metallic iron or nickel inclusions are one of the more distinctive features of HPHT lab-grown diamonds. Such inclusions are made of undissolved flux which solidified as the lab-grown diamond cooled.
Metallic Needles
Commonly seen in HPHT lab-grown diamonds, metallic needles can be large or very fine. They frequently follow the growth pattern of the lab grown crystal, aligning themselves along crystal faces and edges.
Inclusions seen in CVD-grown diamonds
Chemical Vapor Deposition (CVD) causes carbon atoms to rain down on a substrate of diamond seed, growing diamond in vertical layers.
Cometic Remnants
These carbon inclusions, seen in CVD lab grown diamonds, take on a comet-like appearance. They are formed when crystal growth continues after the appearance of dark/opaque inclusions; i.e. non-diamond carbon which subsequently disturbs the continued growth process.
Planar Clouds
Planar Clouds are groups of minute to very small growth remnants which occur on a single geometric plane. Planar clouds form due to stops and starts in the vertical CVD crystal growth process.
HPHT Magnetism
Fun fact: Some HPHT grown diamonds have enough metallic remnants to be picked up with a magnet.
HPHT grown diamonds may also be falsely identified as moissanite by handheld electronic diamond testers, which measure electrical conductivity.
All images are courtesy of IGI
