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identification of natural synthetc and treated diamonds

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anudippal

Rough_Rock
Joined
May 26, 2003
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2
hi! Came on to the site by chance as was searching some answers regarding how to identify natural type 2a diamonds from lab made 2a diamonds and HPHTtreated 2a diamonds . I am a student learning for my exams at the moment . By seeing some of the letters i am sure some of u can give me the right answer which will be a great help to me for my exams.
Thanks Anu.
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Hi Anu. The "SSEF Diamond Type Finder" which Furthermore recommends is handy for distinguishing type 2A diamonds, which are the majority (but not all) of diamonds HPHT color enhanced. It cannot, however, tell the difference between a natural 2A or an HPHT color enhanced 2A. The idea with the SSEF DTF is that if the diamond is not a Type 2A, then the chances are great that it is not HPHT color enhanced as well.

HPHT lab created diamonds can be a different story though. The current crop of HPHT lab created diamonds out on the market from the Gemesis company are mostly Type 1B diamonds. The Gemesis company is in Sarasota and the marketing director is an acquaintance of mine. Consequently I have analyzed a number of their stones, and can talk a bit about how to distinguish them. They're quite beautiful, by the way.

The key to distinguishing the HPHT lab created diamonds, is to realize their growth process. Powdered graphite is dissolved under High Pressure - High Temperature in a molten metal solvent containing nickel, iron & cobalt, among other ingredients. The top part of the unit it is dissolved in is the "hotter" portion, with a small seed diamond crystal being located in the bottom "cooler" portion. This is where the diamond crystalization takes place, upon the seed crystal.

The detection of nickel and cobalt is a positive diagnostic for ID'ing lab created diamonds. In addition to this there are some other strong indicators which point toward the synthetic ID.

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Under observation with a 10x loupe or microscope:

1. Shiny or opaque metallic inclusions. Sometimes triangular in shape. This is diagnostic.
2. Fairly dense clouds of very tiny pinpoint inclusions. These clouds are unlike those seen in type 1A diamonds. Strongly indicative.
3. Narrow, clearly defined color zoning not seen in natural diamonds. The color zoning resembles that seen in Sri Lankan sapphires, with totally clear zoning next to saturated color. Strongly indicative.

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Under longwave and shortwave fluorescence:

1. Often weak to very weak orange fluorescence under both SW/LW, sometimes with an unusual green "cross" or "X" fluorescent figure superimposed against the weak orange fluorescence. This is diagnostic.

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Reaction to rare earth magnet:

Because iron from the flux is often included in the crystals, these stones will sometimes be very weakly attracted to a rare earth magnet. Strongly indicative.

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Personal observations:

These diamonds often have very fine makes, with striking fancy intense to fancy vivid colors. Because they have a depth of color which doesn't require the the cutter to play any "tricks" with the cut to deepen the color, the diamonds are often cut to optimum makes.

The yellows often have a slight green modifying hue to them.

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Visible spectra:

Non-diagnostic

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Advanced instrumentation:

Detection of nickel or cobalt via photo-luminescence spectra is diagnostic.
 
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