Tuesday, 5 April 2016

Lab-Grown Diamonds And How Labs Detect Them

They look like diamonds, they shine like diamonds but they are not diamonds – at least not in the true sense of the word. We are talking about lab-grown diamonds.

Diamond growing began in the 1950’s. It was, and still is, mainly rooted in industrial production.

Companies that manufacture everything from drill bits to semiconductors use lab-grown diamonds. To them, they are perfect because they embody all the necessary diamond traits without being as expensive as their natural counterparts.

Recent technological advancements have made the production process of lab-grown diamonds easier. And this has pushed some producers into the gem trade.

Lab-growing of type IIa/b HPHT (high-pressure, high-temperature) diamonds only hit the market as recently as 2014, according to GIA.

But gemologists are not worried. They say they can totally tell the difference between lab-grown diamonds and natural ones.

Major gem-testing labs around the world use similar procedures to test diamonds to ascertain whether or not they are natural or lab-grown, simulants or treated.

Each lab might use different methods and machines but here’s what they all agree on:

All colorless diamonds first undergo screening and are currently tested to see if they are type Ia — which comprises about 98 percent of all natural white diamonds. Any stone that is determined to be type II will require more testing. Different methods of screening include infrared (IR) spectroscopy, ultraviolet (UV) absorption, UV transparency and photoluminescence (PL) imaging. These machines can identify natural diamonds with about 97 percent accuracy and about 3 percent of natural diamonds will be flagged for further testing. Type Ib diamonds — deep yellow and brown visually — tend to go straight to finalizing processes.

Diamonds flagged for further testing will undergo a finalizing process, where the stones are examined by a person under machines that examine element composition, crystal structures, electromagnetic absorption, phosphorescence and fluorescence, to name a few.

IR spectroscopy measures how different elements in a diamond absorb electromagnetic radiation at different wavelengths. Each type absorbs infrared light at specific wavelengths.

The ultraviolet absorption method, similar to infrared spectroscopy, measures whether the diamonds absorb UV rays at the specific wavelength that type I diamonds do.

The UV transparency method measures whether specific bands of light can pass through a diamond. Natural type Ia diamonds are opaque to this light, while type IIa — which appears colorless — are transparent.

PL imaging comprises testing for fluorescence — how a diamond glows in the presence of UV light — and the strength and duration of phosphorescence — a diamond’s ability to continue glowing after the UV source has been shut off. Natural type Ia diamonds tend to fluoresce blue and do not phosphoresce, and any diamond that glows in other colors or continues glowing are referred for further testing.

Read more from Rapaport Magazine…

Screening machines test for type Ia because current methods of production cannot re-create type Ia diamonds- yet.

Natural diamonds are found in all types — Ia and Ib, IIa and IIb.

HPHT diamonds can only be Ib, IIa and IIb and CVD diamonds are only IIa and IIb. Type I diamonds have detectable nitrogen impurities and type II diamonds do not.

Many of the machines that screen for types might not be as accurate in the near future since producers will gain greater control over the growth process affecting diamond types, says Branko Deljanin, president and head gemologist at the CGL-GRS Swiss Canadian Gemlab.

For now, we can only sit and hope that the day producers will be able to re-create Ia diamonds doesn’t come too soon.



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