How are diamonds made?

Diamonds form naturally deep beneath the Earth's surface, but they can also be made in a laboratory by diamond manufacturers. Read on to learn about the variety of ways in which we can find and produce this highly sought-after gemstone.

Natural diamonds

Natural diamonds are formed from pure carbon at a depth of around 100 miles below the Earth's surface. The process of diamond formation occurs over millions (or even billions) of years within the molten rock of the Earth's mantle, where the right amounts of pressure and heat can be found to transform carbon into diamond. The diamonds are then carried through flows of molten lava to the Earth's surface where it is mined and turned into the precious stones we used to make jewellery.

Synthetic diamonds

There are two ways of making synthetic diamonds in a laboratory, both of which are used by diamond manufacturers. The first synthetic method is known as 'high pressure, high temperature', or HPHT for short. This method is the closest thing to the diamond production process that occurs naturally within the Earth, and involves subjecting graphite (which is made from pure carbon) to intense heat and pressure.

Tiny pieces of metal in the HPHT machine are used to squeeze down the graphite as it is zapped with an intense pulse of electricity. This process takes just a few days and results in a gem-quality diamond. Unfortunately, this type of synthetic diamond is not as pure as a natural diamond, because part of the metallic solution used to form the diamond can become mixed in with the graphite.

The second diamond-producing method is called chemical vapour deposition. This method produces diamonds even more flawless than those found in nature. Chemical vapour deposition involves placing a piece of diamond into a depressurising chamber, where it is treated with a natural gas under a microwave beam. When the gas heats to around 2,000 degrees, carbon items rain down onto the diamond and stick to it. Using this process, manufacturers can grow a perfect sheet of diamond overnight.