1) Static high-pressure high-temperature: This method also has two sub-types – with or without catalysts. The one without catalysts is to directly change graphite to diamonds under super high pressure and temperature. Its requirement for pressure is about 10 GPa, and requirement for temperature is above 3000 K. These requirements are higher than the requirements of the method with catalysts by about 1 time.

2) Dynamic high-pressure high-temperature: This method is also called explosive method, which changes graphite to diamond grains of micron sizes under instantaneous super high pressure and temperature which are generated and disappear very quickly. The pressure can reach 1000 GPa, and the time is only a few hundred microseconds.

3) Chemical Vapor Deposition (CVD): This method grows diamonds at low pressures (133 Pa – 106 kPa) and non-high temperatures (500 – 800°C). By this method, a hydrocarbon gas mixture is ionized into chemically active radicals to form diamonds. The advantages of CVD diamond growth include the ability to grow diamond over large areas and on various substrates, and the fine control over the chemical impurities and thus properties of the diamonds produced.

1) High hardness, high wear resistance: Diamond has the highest hardness value. Its abrasive hardness is 150 times of corundum, 1000 times of quartz and 6 times of carbide alloy.

2) Low friction coefficient: The friction coefficient between diamond and metal in the air is 0.1. Therefore, diamond has a very high frictional resistance. Its friction resistance is 90 times of corundum, 100 times of carbide alloy and 9000 times of steel.

3) High strength: Diamond’s crystal structure, its Impurity’s composition and content determine the strength of a diamond. Natural diamond’s compressive strength is about 8000 kg/cm², which is about 3.5 times of corundum, 1.5 times of carbide alloy and 9 times of steel.

4) Though diamond has high hardness and high strength, it also has brittleness. When a diamond receives a certain degree of impact force, it may generate cracks or even be broken into regular-shape small pieces. This is the biggest weakness of diamond.

5) High thermal conductivity, bad thermal stability: The change of temperature has a fairly big influence on the strength of diamond. With the rise of temperature, diamond’s strength declines.

8.2 mm, 2 carats synthetic diamond made by Henan Polytechnic University (China).

Diamonds can be synthesized or be so called “cultured” in man-made environments, and the synthetic diamonds can be the same with or even better than natural diamonds. Gemesis, the world’s leading gem quality synthetic diamonds producer in Florida, USA, says: “Gemesis cultured diamonds are at the forefront of a revolution in the diamond jewelry industry. A Gemesis cultured diamond is a diamond, grown under the same conditions as diamonds grow beneath the earth’s surface. By applying tremendous heat and pressure, a diamond begins to grow, atom by atom, layer by layer, just as it does in nature. A Gemesis cultured diamond possesses the same physical, optical and chemical properties as earth-grown diamonds.”

Yellow synthetic diamond gemstones made by Gemesis, a company in Florida, USA.

It was said that the production cost of a Gemesis cultured diamond is less than 1% of the price of a same natural diamond. Gemesis is producing big diamond gemstones in huge quantity. Also, its diamonds’ color can be yellow, pink, blue, green, or even red, which are rare in the nature and are known as “fancy color”.

Cultured yellow diamonds surround a pink diamond. Made by Gemesis.

It was reported that one of the leading synthetic diamond manufacture companies in China is also researching gem quality synthetic diamonds and already can produce 6mm ones. This company used to produce small synthetic diamonds for diamond tools.

The market’s responses to synthetic diamond gemstones are active. A jeweler in USA said: “If you go into a florist and buy a beautiful orchid, it’s not grown in some steamy hot jungle in Central America; it’s grown in a hothouse somewhere in California. But that doesn’t change the fact that it’s a beautiful orchid.” “Nobody cares if it’s from De Beers. My clients just want a nice diamond.”

With the same or even better but much cheaper synthetic diamond gemstones’ emerging on the jewelry market, it can be anticipated that the natural diamond gemstones will have no advantages and their values will decrease dramatically. If you have natural diamond gemstones or have investments on them, you will have to be prepared.

Colorless gemstone cut from diamond grown via another method called “CVD” (Chemical Vapor Deposition) by Apollo Diamond, a company in Boston, USA.