Gemologist Studying Diamonds

Inclusions Seen in Lab Grown Diamonds

There are two sophisticated ways of producing lab grown diamonds. The first is the High-Pressure High Temperature (HPHT) method, where heavy mechanical presses and intense heat are combined to replicate the conditions under which natural diamonds formed. The second is Chemical Vapor Deposition (CVD), a process that superheats gas into plasma, releasing carbon atoms to ‘build’ a diamond crystal at the atomic level.

Both of these methods grow diamonds which are optically, chemically and physically identical to natural diamonds. However, one process assembles the diamond in vertical layers and the other uses a metal catalyst to dissolve component carbon. These different approaches produce inclusions which differ from those seen in natural diamonds. These inclusion types are important to recognize when grading lab grown diamond clarity, one of the value-setting 4Cs of diamonds.

Watch: IGI Explains Lab Grown Diamonds

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.

IGI Inclusion Photograph
Photography by IGI

 

IGI Inclusion Photograph
Photography by IGI

‘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.

IGI Inclusion Photograph
Photography by IGI

 

IGI Inclusion Photograph
Photography by IGI

‘Dendritic Remnants’

Relatively uncommon, branchlike dendritic inclusions can resemble trees or bushes when dark, or snow-covered branches when light. They occur when flux, still in its molten state, becomes trapped by the growing crystal.

IGI Inclusion Photograph
Photography by IGI

 

IGI Inclusion Photograph
Photography by IGI

Inclusions seen in CVD-grown diamonds

As you saw in the video at the beginning of this article, 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.

IGI Inclusion Photograph
Photography by IGI

‘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.

IGI Inclusion Photograph
Photography by IGI

 

IGI Inclusion Photograph
Photography by IGI

‘Internal Graining’

Also referred to as Stria, Internal Graining shows as reflective angles or lines, that may appear whitish, colored or reflective, caused by stops and starts in the vertical CVD crystal growth process.

IGI Inclusion Photograph
Photography by IGI

 

Inclusions seen in both natural and lab grown diamonds

  • Bruise – A small area of impact, accompanied by tiny feathers
  • Cavity – A large or deep opening in the gemstone
  • Chip – A shallow opening in the gemstone
  • Cleavage – A crack in the gemstone which is parallel to one of its crystallographic planes
  • Cloud – A group of minute to very small growth remnants which give a “cloudy” appearance
  • Feather – A fracture or break in a diamond that may resemble a white feather
  • Pinpoint – A tiny dotlike growth remnant

Blemishes seen in both natural and lab grown diamonds

While some blemishes are caused by polishing, most are caused by wear after sale to an end consumer.

  • Abrasion – A series of minute nicks along the facet junctions
  • Burn Mark – Hazy area caused by excessive heat or uneven polishing
  • Extra Facet – A facet not required by the cutting style, placed without regard to symmetry
  • Nick – A small notch on a facet junction with no apparent depth
  • Pit – A small opening that looks like a tiny white dot
  • Polish Lines – Parallel ridges left by the polishing process
  • Scratch – A thin white line across the gemstone’s surface

Surface Remnants seen in lab grown diamonds

These are essentially the same as Naturals and Indented Naturals, seen in natural diamonds.

  • Surface Remnant – A portion of the lab grown rough stone that was left unpolished
  • Indented Surface Remnant – A portion of the lab grown rough stone that dips below the polished gemstone’s surface

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. Learn more about this, and other false positives, in our post covering Diamond Detection and Handheld Testers.

IGI Inclusion Photograph
Photography by IGI

 

John Pollard

John Pollard is Senior Director of Education for IGI, overseeing and expanding the institute’s traditional educational offerings and diploma programs, instructed at 14 schools of gemology around the world, along with customized eLearning courses, tutorials, seminars, and webinars for IGI clients across all sectors, including leading luxury brands.

This Post Has 4 Comments

  1. Arun

    Can I educate my customers on Lab Growns from the video you have added to my website?

    Let me know how I can go about this.

    1. John Pollard

      Hello Arun. Yes, you are free to use the embed tool to stage the video on your website. All we ask is attribution, such as “Courtesy of IGI.” Thank you.

  2. SANDY GALA

    NICKEL IRON, ALUMINUM, CHEMICAL VAPOR, PLANAR CLOUDS, ALSO NITROGEN GASES ARE ALSO FOUND IN DIAMONDS OF CELESTIAL ORIGIN. THERMAL TESTERS ARE USELESS FOR DETECTING ROUGH TYPE 2 B DIAMONDS. THE NORMAL TESTER IS BASED ON LIGHT REFRACTION IF THE STONE HAS NOT BEEN CUT TO THE BASIC 57 FACETS IT ALSO IS USELESS FOR ROUGH. PLEASE CORRECT ME IF I AM WRONG (SMILE )

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