How a diamond grows in four weeks

Ask most jewelers where their diamonds come from and you will get a region, not an answer. Ours come from a room we own, and the process takes about four weeks. Here is what actually happens in it.

It starts with a slice of diamond

Every diamond we grow begins as a seed plate, a wafer of diamond perhaps two millimeters thick, cut flat and polished to a mirror. Nothing grows from nothing. The seed gives the carbon atoms a lattice to copy, and the quality of that seed sets a ceiling on the quality of everything that follows. A flawed seed grows a flawed stone.

The plate goes into the reactor on a holder, dozens at a time, and the chamber is pumped down to near vacuum.

Then hydrogen, methane, and a great deal of energy

CVD stands for chemical vapor deposition, which sounds more mysterious than it is. We fill the chamber with hydrogen and a small amount of methane, then use microwaves to heat the gas until it becomes a plasma: a glowing ball suspended above the seed plates, hot enough that the methane molecules come apart.

Freed carbon atoms drift down and settle onto the seed. If conditions are right, they lock into the diamond lattice already there and extend it. Layer by layer, atom by atom, the plate grows thicker.

The hydrogen is doing something clever in the background: it preferentially etches away any carbon that tries to form as graphite rather than diamond. Without it you would grow soot. With it, you grow a crystal.

Four weeks of not touching anything

Growth runs continuously for roughly three to four weeks depending on the size we want. The hardest part is leaving it alone. Temperature, pressure and gas ratios have to stay within a narrow band the entire time; drift too far and you get inclusions, strain, or a brown tint that no amount of later polishing will remove.

This is the real reason a grower's experience matters. The science is published and the machines can be bought. Knowing what a run looks like when it is subtly going wrong, at hour four hundred, is not in any paper.

Out of the reactor, into the cutter's hands

What comes out is a rough crystal, cloudy on the surface and nothing like the stone you would recognize. It is measured, mapped for inclusions, and planned: the cutter decides what shape will yield the best stone from that particular piece of rough, which is exactly the calculation made on a mined crystal.

Then it is cut and polished by hand on a wheel, the same way diamonds have been finished for a century. No one has found a better method.

And then we send it away to be judged

Finished stones go to an independent laboratory such as IGI or GIA, with no stake in what we sell. They measure it, assess the cut, color and clarity, laser-inscribe the report number on the girdle, and send it back with a report we had no hand in writing.

We think that last step is the whole point. Anyone can describe their own diamond generously. The report is the part you can check.

We run more than five hundred reactors. Every stone we set began as a seed plate in one of them, which means that when you ask us where a diamond came from, we can tell you.

See what those stones become: engagement rings, diamond studs and tennis bracelets. Or read lab-grown vs natural diamonds: what is actually different.