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A Guide
Information & images from GIA
A laboratory-grown diamond (left) and a natural diamond (right) can appear identical to the naked eye.
Natural diamonds formed deep in the earth under extreme pressure and high temperature as long as three billion years ago. Volcanic activity brought them to the surface where they lay in a type of volcanic rock formation known as kimberlite pipes, waiting to be mined. Only about five percent of kimberlite pipes contain enough diamond to make them economically feasible to mine.
Open pit of the Arkhangelskaya kimberlite in Lomonosov, Russia. Photo: Karen Smit/GIA
Man-made diamonds suitable for industrial use were first produced in a laboratory in the 1950s. While gem-quality diamonds were produced in a laboratory for the first time in 1971, it was not until the mid-2010s that colourless laboratory-grown diamonds entered the gem and jewellery market in commercial quantities.
Today, laboratory-grown diamonds are created by two methods, according to Dr. James Shigley, GIA Distinguished Research Fellow, who has been researching laboratory-grown diamonds at GIA for more than 30 years.
High pressure, high temperature (HPHT) diamonds are produced in a laboratory by mimicking the high pressure, high temperature conditions that form natural diamonds in the Earth. This process produces a distinctively shaped laboratory-grown diamond crystal.
The chemical vapor deposition (CVD) method involves breaking down the molecules of a carbon-rich gas, such as methane, into carbon and hydrogen atoms, which then are deposited on diamond seeds to produce a square-shaped, tabular diamond crystal.
Growing diamonds by either method typically requires less than a month for most sizes. Most CVD-grown diamonds require additional treatments like heat or irradiation to enhance or change their colours after the growth process.
Typically, laboratory-grown diamonds have weighed a carat or less, but as technology and techniques improve, larger stones have appeared in the market.
HPHT (High-Pressure and High-Temperature) presses enclosed in a factory which can produce gem-quality diamonds within a large range of sizes. Photo: Wuyi Wang/GIA
It is essential that laboratory-grown diamonds can be identified because consumers need to know what they are buying, and because there are often significant price differences between them and natural gemstones.
Because laboratory-grown diamonds are essentially chemically and optically the same as their natural counterparts, traditional gemological observations and old-style “diamond detectors” are not able to tell them apart. Identification at a professional gemological laboratory or using sophisticated devices developed by GIA and other organisations are the only reliable methods to separate them from natural diamonds.
Diamond Morphology – the Telltale Factor
“Natural diamonds that formed in the Earth over millions of years grow differently from diamonds created in a laboratory in a few weeks. In addition, HPHT- and CVD-created diamonds have different growth morphology, or how growth conditions influenced the shape of the diamond crystal,” said Dr. Shigley.
GIA Senior Research Scientist Dr. Sally Eaton-Magaña further explained, “The identification criteria for HPHT and CVD diamonds are quite distinct from each other,” adding that laboratory-grown diamonds have become much more varied over the last 10 to 15 years, requiring GIA researchers to keep pace with new developments.
ENVIRONMENTAL INFORMATION
Every manufacturing industry, including natural and laboratory-grown diamond, has a carbon footprint.
Natural production : the Argyle mine uses 7.5kWh to recover a 1 carat diamond
Laboratory-Grown Production : Genesis diamond used 20kWh for a normal growth run.
There are also socio-economic considerations that are important in evaluating the mining and manufacturing of diamonds..