A worker breaks open a grey block and retrieves sparkling crystals from the fragments. These are lab-grown diamonds, made in a Chinese factory. Once cut, they can look just like a diamond from the earth to the naked eye.
The footage from China shows a striking side of lab-grown diamonds. This is not a matter of pouring a shiny stone into a mould. Manufacturers grow carbon into diamond under controlled conditions. Large machines create an extremely intense environment in a tiny space.
A tiny seed inside an enormous press
One common method is called HPHT: high pressure and high temperature. According to the Gemological Institute of America, GIA, this involves around 1,300 to 1,600 degrees Celsius and a pressure of five to six gigapascals. That is roughly 50,000 to 60,000 bar.
A capsule contains a carbon source, metal and a small diamond crystal that acts as a seed. The metal helps dissolve the carbon. Carbon can then deposit on that tiny diamond seed, allowing the crystal to grow. The press provides the force; the precisely controlled conditions do the growing.
That takes considerably longer than the hammer blows at the end. GIA gives HPHT growth times ranging from about an hour to several weeks, depending on the size and quality required. Breaking open the block reveals the result; it is not what forms the diamond.
Lab-grown does not mean imitation glass
A factory-grown diamond has the same carbon crystal structure as a natural diamond, GIA explains. Its chemical, optical and physical properties are therefore almost the same. The main difference lies in how it formed: inside the earth or in a growth chamber.
That is different from an imitation stone that only looks like diamond. Glass and cubic zirconia can sparkle too, but they are different materials. Specialist laboratories can use instruments to investigate how a diamond grew; the naked eye cannot reliably distinguish a lab-grown diamond from a natural one.
Why there are so many machines
Production has become an industry. GIA research describes Chinese manufacturers using HPHT to mass-produce small diamonds. The technology was already used to make diamond grit and powders for grinding and cutting, and developed further towards jewellery quality.
The rough crystals produced by growth are not ready-made ring stones. Selection, cutting and polishing still follow. But the essential material is already there. That is what makes this factory remarkable: a stone we associate with deep mines can also grow in a capsule between steel presses.
