How the laboratory-grown diamond began: the morning of 16 December 1954

A paper read on 15 December 1796

Isaac Newton noticed that a mined diamond bends light more strongly than its density would suggest, as substances that burn tend to, and guessed that it might burn. Long after Newton, the guess became an experiment. On 15 December 1796 the English chemist Smithson Tennant read a paper to the Royal Society in London. He had heated a mined diamond with nitre, caught the gas it gave off, and found it gave about the same amount as an equal weight of charcoal. His conclusion was blunt: the stone was charcoal, “differing … only by its crystallized form”.

Knowing the ingredient turned out to be the easy half. Carbon was everywhere, in soot and in the graphite of a pencil. Arranging it into that crystal was the hard part, and for more than a century nobody managed it in a way someone else could repeat. In the 1890s the French chemist Henri Moissan claimed to have grown the first laboratory-grown diamond in his electric furnace. Other experimenters couldn’t reproduce it.

Moissan is remembered instead for a find of 1893: crystals in rock samples from Meteor Crater, near Canyon Diablo in Arizona, that he first took for the very stone he was trying to make. In 1904 he showed they were silicon carbide, the mineral later named moissanite in his honour. They were not diamonds, and moissanite still isn’t one. It is the subject of the next lesson.

Rubber boots and a ring of steel

In 1951, General Electric restarted its own attempt at its laboratories in Schenectady, New York, forming a high-pressure group with Francis Bundy and H. M. Strong. Among the GE scientists was H. Tracy Hall. For a time he worked at a 35-year-old press that leaked so much hydraulic water that he wore rubber boots beside it. He also designed an apparatus of his own: a ring of hardened steel, strained right up to the point where steel stops springing back, wrapped round a small sample. He called it the belt, and it could reach pressures above 10 gigapascals and temperatures above 2,000 °C.

On the morning of 16 December 1954, a run held carbon with a metal catalyst at about 100,000 atmospheres and 1,600 °C. When Hall looked at the result, he saw dozens of tiny crystals flashing in the light.

“My hands began to tremble; my heart beat rapidly.”

H. Tracy Hall, remembering that morning

They were small. The largest of Hall’s crystals was about 0.15 mm across, too small for jewellery, though useful as an industrial abrasive. That didn’t matter. What made the morning history was that the process could be repeated, and it was: the first laboratory-grown diamond made by reproducible means that others could verify. GE announced it in February 1955.

There is a footnote, and a fair account includes it. On 16 February 1953 a team at the Swedish electrical company ASEA had already made crystals in Stockholm, in an apparatus designed by Baltzar von Platen and Anders Kämpe. They didn’t report it, and their result was announced only after GE’s.

From grit to gems, and a second road

Gems took longer. GE grew its first gem-quality crystals in 1970, by the same high-pressure route, and reported them in 1971.

By then a second road was open. In the early 1950s, at Union Carbide, William Eversole had deposited laboratory-grown diamond from a carbon gas onto a seed crystal; GIA dates the first documented growth to 1952. This is chemical vapour deposition, or CVD: carbon from a gas, laid down at pressures below that of the air we breathe, building a crystal in thin layers. By 2003, GIA’s journal Gems & Gemology was describing gem-quality CVD crystals a few millimetres thick and up to a carat or more: near-colourless to brown, and Type IIa, a term we will come back to.

The road to your stone, in ten dates

1. 1796

   Smithson Tennant’s paper: a mined diamond is nothing but carbon.

2. 1893

   Henri Moissan finds crystals in rock from Meteor Crater, Arizona; in 1904 he shows they are silicon carbide.

3. 1951

   General Electric forms its high-pressure group in Schenectady.

4. 1952

   William Eversole’s growth from a gas, the first step to CVD, is documented.

5. 1953

   16 February: ASEA makes crystals in Stockholm, and doesn’t report them.

6. 1954

   16 December: H. Tracy Hall’s run in the belt, the first that others could repeat.

7. 1955

   February: GE announces it.

8. 1970

   GE grows the first gem-quality crystals, reported in 1971.

9. 2003

   Gems & Gemology describes gem-quality CVD crystals.

10. 2021

    January: IGI reports begin to say whether a stone is “as grown”.

Two ways to grow a crystal

Every laboratory-grown diamond today comes from one of those two roads. Both start from a seed crystal for the new one to grow on, and both need carbon and heat. What differs is how the carbon reaches the seed.

HPHT and CVD, side by side

Feature	HPHT	CVD
Stands for	High pressure, high temperature	Chemical vapour deposition
The idea	Recreate the conditions deep underground	Build the crystal from a gas, layer on layer
Pressure	5–6 gigapascals	Below the pressure of the air
Heat	1,300–1,600 °C	About 900–1,200 °C
The carbon	High-purity carbon dissolved in molten metal	Methane, with hydrogen, broken up by a microwave plasma
Time to grow	An hour to a few weeks	Three or four weeks
After growth	Cut and polished; a report says if a stone was treated	About 80% of the CVD stones submitted to GIA had been annealed after growth, at high temperature with or without high pressure, to improve their colour

Either way, what comes out has, in GIA’s words, essentially the same chemical, physical and optical properties as a mined diamond, which is why a report from an independent laboratory states the origin plainly. How the two are told apart is the subject of the first lesson in this path, laboratory-grown or mined diamond.

What the method means for your stone

On an IGI report, the growth method is a line of fact, not a grade. Since January 2021, IGI has also said whether a laboratory-grown stone is “as grown” or may have been treated after growth. The IGI report shown on our homepage, LG813625650, describes an 8.07 ct oval as “CVD grown, Type IIa”. Type IIa means there is no measurable nitrogen in the crystal. Underground that is rare: GIA reports that only about 1 per cent of mined diamonds are type II at all.

The method doesn’t tell you how a stone looks. Cut, clarity and colour do, and clarity and colour have lessons of their own later in this path. Every laboratory-grown diamond we set is E–F colour and VVS–VS clarity, main stones and the smallest pavé alike, and a laboratory-grown main stone above 1 carat comes with its own IGI report in the box.

One last consequence of all this history is in the words. India’s standard IS 19469:2025 allows the word diamond for stones like these only with “laboratory-grown” or “laboratory-created” in front of it, which is why you will always see us write the full term.

See it in a piece

Three of our rings, and where the report begins.

Check yourself

Three questions. Tap one to see the answer.

Next in this path

Lesson 3: Laboratory-grown diamond or moissanite: which to choose

Read lesson 3

1. Laboratory-grown or mined diamond: what is actually different
2. How the laboratory-grown diamond began: the morning of 16 December 1954You are here
3. Laboratory-grown diamond or moissanite: which to choose
4. VVS and VS clarity: what “very slightly included” looks likeComing later
5. E and F colour: what “colourless” means on a reportComing later
6. What an IGI report shows
7. What decides the price of a laboratory-grown diamond ring