In the early stages of diamond synthesis, the founding figure of modern chemistry,
Antoine Lavoisier, played a significant role. His groundbreaking discovery that a diamond's crystal lattice is similar to carbon's crystal structure paved the way for initial attempts to produce diamonds. After it was discovered that diamond was pure carbon in 1797, many attempts were made to convert various cheap forms of carbon into diamond. The earliest successes were reported by
James Ballantyne Hannay in 1879 and by
Ferdinand Frédéric Henri Moissan in 1893. Their method involved heating
charcoal at up to with iron inside a
carbon crucible in a furnace. Whereas Hannay used a flame-heated tube, Moissan applied his newly developed
electric arc furnace, in which an electric arc was struck between carbon rods inside blocks of
lime. The molten iron was then quenched by immersion in water to induce rapid cooling. The contraction generated by the cooling supposedly produced the high pressure required to transform graphite into diamond. Moissan published his work in a series of articles in the 1890s. Many other scientists tried to replicate his experiments. Sir
William Crookes claimed success in 1909.
Otto Ruff claimed in 1917 to have produced diamonds up to in diameter, but later retracted his statement. In 1926, Dr.
J. Willard Hershey of
McPherson College replicated Moissan's and Ruff's experiments, producing a synthetic diamond. Despite the claims of Moissan, Ruff, and Hershey, other experimenters were unable to reproduce their synthesis. The most definitive replication attempts were performed by Sir
Charles Algernon Parsons. A prominent scientist and engineer known for his invention of the
steam turbine, he spent about 40 years (1882–1922) and a considerable part of his fortune trying to reproduce the experiments of Moissan and Hannay, but also adapted processes of his own. Parsons was known for his painstakingly accurate approach and methodical record keeping; all his resulting samples were preserved for further analysis by an independent party. He wrote a number of articles—some of the earliest on HPHT diamond—in which he claimed to have produced small diamonds. However, in 1928, he authorized Dr. C. H. Desch to publish an article in which he stated his belief that no synthetic diamonds (including those of Moissan and others) had been produced up to that date. He suggested that most diamonds that had been produced up to that point were likely synthetic
spinel. Pressure was maintained within the device at an estimated and a temperature of for an hour. A few small diamonds were produced, but not of gem quality or size. Due to questions on the patent process and the reasonable belief that no other serious diamond synthesis research occurred globally, the board of ASEA opted against publicity and patent applications. Thus the announcement of the ASEA results occurred shortly after the GE press conference of February 15, 1955.
GE diamond project In 1941, an agreement was made between the
General Electric (GE),
Norton and
Carborundum companies to further develop diamond synthesis. They were able to heat carbon to about under a pressure of for a few seconds. Soon thereafter, the
Second World War interrupted the project. It was resumed in 1951 at the
Schenectady Laboratories of GE, and a high-pressure diamond group was formed with
Francis P. Bundy and H. M. Strong.
Tracy Hall and others joined the project later. and the diamond was later shown to have been a natural diamond used as a seed. Hall achieved the first commercially successful synthesis of diamond on December 16, 1954, and this was announced on February 15, 1955. His breakthrough came when he used a press with a hardened steel
toroidal "belt" strained to its elastic limit wrapped around the sample, producing pressures above and temperatures above . The press used a
pyrophyllite container in which graphite was dissolved within molten
nickel,
cobalt or iron. Those metals acted as a "solvent-
catalyst", which both dissolved carbon and accelerated its conversion into diamond. The largest diamond he produced was across; it was too small and visually imperfect for jewelry, but usable in industrial abrasives. Hall's co-workers were able to replicate his work, and the discovery was published in the major journal
Nature. He was the first person to grow a synthetic diamond with a reproducible, verifiable and well-documented process. He left GE in 1955, and three years later developed a new apparatus for the synthesis of diamond—a tetrahedral press with four anvils—to avoid violating a
U.S. Department of Commerce secrecy order on the GE patent applications.
Further development Synthetic gem-quality diamond crystals were first produced in 1970 by GE, then reported in 1971. The first successes used a pyrophyllite tube seeded at each end with thin pieces of diamond. The graphite feed material was placed in the center and the metal solvent (nickel) between the graphite and the seeds. The container was heated and the pressure was raised to about . The crystals grow as they flow from the center to the ends of the tube, and extending the length of the process produces larger crystals. Initially, a week-long growth process produced gem-quality stones of around (1
carat or 0.2 g), and the process conditions had to be as stable as possible. The graphite feed was soon replaced by diamond grit because that allowed much better control of the shape of the final crystal. The first gem-quality stones were always yellow to brown in color because of contamination with
nitrogen.
Inclusions were common, especially "plate-like" ones from the nickel. Removing all nitrogen from the process by adding aluminum or
titanium produced colorless "white" stones, and removing the nitrogen and adding
boron produced blue ones. Removing nitrogen also slowed the growth process and reduced the crystalline quality, so the process was normally run with nitrogen present. Although the GE stones and natural diamonds were chemically identical, their physical properties were not the same. The colorless stones produced strong
fluorescence and
phosphorescence under short-wavelength ultraviolet light, but were inert under long-wave UV. Among natural diamonds, only the rarer blue gems exhibit these properties. Unlike natural diamonds, all the GE stones showed strong yellow fluorescence under
X-rays. The
De Beers Diamond Research Laboratory has grown stones of up to for research purposes. Stable HPHT conditions were kept for six weeks to grow high-quality diamonds of this size. For economic reasons, the growth of most synthetic diamonds is terminated when they reach a mass of . Diamond film deposition was independently reproduced by Angus and coworkers in 1968 and by Deryagin and Fedoseev in 1970. Whereas Eversole and Angus used large, expensive, single-crystal diamonds as substrates, Deryagin and Fedoseev succeeded in making diamond films on non-diamond materials (
silicon and metals), which led to massive research on inexpensive diamond coatings in the 1980s. From 2013, reports emerged of a rise in undisclosed synthetic melee diamonds (small round diamonds typically used to frame a central diamond or embellish a band) being found in set jewelry and within diamond parcels sold in the trade. Due to the relatively low cost of diamond melee, as well as relative lack of universal knowledge for identifying large quantities of melee efficiently, not all dealers have made an effort to test diamond melee to correctly identify whether it is of natural or synthetic origin. However, international laboratories are now beginning to tackle the issue head-on, with significant improvements in synthetic melee identification being made. The largest synthetic uncut diamond is 150.42 carats, achieved by Meylor Global LLP (UK) and Dr. Andrey Katrusha (Ukraine) in Kyiv, Ukraine, verified on 16 November 2021. The finished diamond measures 28.55 x 28.25 x 22.53 mm. == Manufacturing technologies ==