What is synthetic diamond? How does it differ from the natural one?

Natural diamonds are formed in the earth at a very high temperature and in depth. They are made of carbon. They will have a crystal structure. They are formed in the earth many millions of years ago,
Synthetic diamonds will be created in the laboratory. They will be made by High-Pressure High-temperature (HPHT) or through commonly used Chemical Vapour Deposition (CVD(. They will be designed to look like real diamonds.
Synthetic Diamonds will be commercially available in yellow colour. The yellow colour is due to nitrogen impurities in the manufacturing process. Synthetic stones will be produced in blue, green or pink colours, which can be obtained by the addition of boron or by irradiation.
Synthetic diamonds are less expensive and they are being produced at a commercial level.
Natural diamonds will have internal flaws which will occur during the formation stage. But Synthetic diamonds will look cleaner. This is because the process through which synthetic diamonds are made are designed to bring down these flaws.
Synthetic diamonds are identical to real diamonds. But sometimes they even will have a superior clarity than natural diamonds. So it is very difficult even to an experienced person to identify the natural one from synthetic material. So many jewellers use spectroscopic devices and techniques to differentiate between synthetic and natural diamonds. So it is better always to ask for a graded certificate from a recognized gemological institute. It is the best way to know whether the diamond is natural or synthetic.

Synthetic diamonds are produced in high temperature and high pressure conditions by injecting a gas vapour on a diamond seed. The commercial synthetic diamonds now a days are like original natural diamonds only. Though the natural diamonds are created deep inside the earth by pressures of the overburden rocks and the process is a lengthy one and takes a long interval before diamonds are formed. These natural diamonds have some impurity also and depending on that, their clarity, colour and texture will be manifested.

It is difficult for a layman to identify the synthetic diamond from the natural one but jewellers have specific tools for the purpose and they can differentiate it.

A. What are synthetic diamonds

Diamonds are compared to coal sometimes because both have the basic component that is carbon. But the rest are totally different. In a very simple terms, heat and pressure(725,000 pounds per square inch) pushes the carbon atoms to fuse and then form diamonds.This process takes several thousand years and many miles beneath us deep within the Earth's crust.

Now scientist can re-create this process and over a few weeks we can make synthetic diamonds.The common process used is known as Chemical vapour deposition.

So, yes, diamonds are being produced commercially. These are referred to as Cultured or Lab diamonds.
B. How to differentiate?

The truth of the matter is that even trained/ experienced find it difficult to assess a diamond with regards to
being natural or synthetic

1. First, we need to be clear on the fact that Synthetic diamonds are not fake because they are diamonds, only the process and composition is different.

2.Flaws and clarity: Ironically, the term flawless natural diamonds can be applied to only few of the naturally mined ones. This is because, natural diamonds have flaws or inclusions within them, this can be modified or minimized in the synthetic creation process. So, a flawless diamond need not be the only criteria.

3.Scratch test: this is based on the hardness but can be destructive to the stone.

4. Thermal conductivity: diamonds are known to have a high thermal conductivity. This can be measured using
thermistor probes, but between synthetic vs natural, we need more advanced optical instruments, spectroscopy etc for proper assessment.

5.Commerical organisations use the services of professional techniques for testing diamonds.

a.One such example is the D-Screen device ( developed by HRD Antwerp and WTOCD).
b. Alpha diamond analyser (developed by HRD Antwerp and Bruker).
c. The Diamond Trading Company (DTC) of De Beers, has also two similar detection devices referred to as DiamondSure and DiamondView.

6. Cost: Again , this alone cannot be used to differentiate because some synthetic diamonds cost only 10% less than a natural diamond. As a general statement natural ones are around 20-40% more expensive than synthetic ones.

C.What is the practical way?

Given the above difficulties and complexity, we need to insist on a authenticity certificates from the manufacturer themselves. A flawless, crystal clear, coloured stone is often a synthetic one because a coloured (blue, red, yellow) natural diamond is very rare and hence very expensive.