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Unique characteristics in laboratory-grown diamonds


With sincere thanks to GCAL USA for permission to share these photos.

HPHT process

HPHT replicates the natural conditions under which diamonds formed. A carbon source, a diamond seed and a metallic catalyst are heated near 1,500 C and subjected to staggering pressure in a press. The melting metal dissolves the carbon and the pressure causes precipitation to the diamond seed, growing a larger diamond. More thorough information can be found on our Laboratory-grown diamonds education page.

Since a metal catalyst is used some clarity characteristics present take on a decidedly metallic appearance.

Inclusions frequently seen in HPHT grown synthetic-diamonds

By far the most frequent characteristics are opaque metallic inclusions, a remnant of their origin in molten metal flux.

A magnified view of the metallic inclusions from the previous photo.

Rod shaped metallic flux inclusions of varying sizes are frequently seen in HPHT grown synthetic-diamonds. Flat, tabular or vaguely triangular shapes are common.

A magnified view shows the unique reflective luster of the metallic flux inclusion from the previous photo.

When metallic flux inclusions are significant enough, the iron and nickel content reveals itself in the form of magnetism. The laboratory-grown origin of this 0.01 carat HPHT grown synthetic-diamond is verified by its attraction to a magnet.

Occasionally thin hair-like needles are present in HPHT grown synthetic-diamonds.

Another example of a metallic flux inclusion in a HPHT grown synthetic-diamond, lighted from behind.

Another example of a metallic flux inclusion in a HPHT grown synthetic-diamond.

Another example of a metallic flux inclusion in a HPHT grown synthetic-diamond.

Black & white dendrite-like inclusions are also present in HPHT grown synthetic-diamonds.

Black & white dendrite-like inclusions are also present in HPHT grown synthetic-diamonds.

CVD process

The CVD process releases carbon atoms from plasma. The atoms descend to land on a flat wafer of previously grown HPHT synthetic diamond. Since they grow in vertical layers striation is created which causes variation in the material's refractive index, as well as clues to their synthesized origin. More thorough information can be found on our Laboratory-grown diamonds education page.

Inclusions frequently seen in CVD grown synthetic-diamonds

A cloud of black inclusions on a single plane shows the layered growth and stop-start cycles of CVD synthesis.

A planar cloud of small whitish inclusions with 'tails' provides a clue to the direction of growth of this CVD produced synthetic-diamond. This feature likely developed during the stop-start growth cycle.

A comet-like tail formed when layered growth continued after the appearance of a black inclusions disturbed the formation of this CVD grown synthetic-diamond.

A comet-like tail formed when layered growth continued after the appearance of a black inclusions disturbed the formation of this CVD grown synthetic-diamond.

A single sharp plane of graining is familiar in faintly colored CVD grown synthetic-diamonds. Although origin identification cannot be proven soley on planar inclusions and graining, they are distinct remnant of CVD's layered growth process and clues as to their synthesized origins.

A single sharp plane of graining is familiar in faintly colored CVD grown synthetic-diamonds. Although origin identification cannot be proven soley on planar inclusions and graining, they are distinct remnant of CVD's layered growth process.

Feathers are common in CVD grown synthetic-diamonds. Their appearance can usually be described as bright, whitish, frosted or thick.

Feathers are common in CVD grown synthetic-diamonds. Their appearance can usually be described as bright, whitish, frosted or thick.

While not helpful in providing assistance in origin identification, a series of bright white feathers in CVD grown synthetic-diamonds are a familiar scene. 

A more magnified view of the feather series pictured above.

Black inclusions ranging in size from pinpoints to large 'crystals' (misnomer) are a common feature in CVD grown synthetic-diamonds. These characteristics are likely collections of carbon atoms which did not precipitate to growth.

Black inclusions ranging in size from pinpoints to large 'crystals' (misnomer) are a common feature in CVD grown synthetic-diamonds. These characteristics are likely collections of carbon atoms which did not precipitate to growth.

The synthetic-diamond landscape remains new. Further content will be added as we discover it.

More thorough information can be found on our Laboratory-grown diamonds education page.

Laboratory-grown diamonds

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