Beryl

The name beryl travelled a long way before it reached us. It came into Middle English as beril, through Old French and Latin beryllus, from the Ancient Greek bḗryllos — a word the Greeks used loosely for a range of blue-green stones. Further back the trail leads east, possibly to the Prakrit veruḷiya or veḷuriya — meaning "beryl" — and from there, by one well-supported guess, to the name of Belur, a town in Karnataka in southern India.

In antiquity the stone was prized as a gem rather than studied as a mineral. The deep green variety we now call emerald was mined in Egypt from around 1500 BCE at a place the Romans named Mount Smaragdus, in the eastern desert. The Egyptian workings were later run on an industrial scale by the Roman and Byzantine Empires, and again by Islamic conquerors after them; mining there ceased only when Spanish ships brought back the much richer Colombian deposits. Pliny the Elder described these green stones in his Natural History, finished in 77 CE — the date the page header records for beryl's earliest written notice.

For nearly two more millennia, emerald, aquamarine, and the colourless and yellow stones we now group together were treated as separate gems. They were sorted by colour, not by chemistry.

Beryllium found inside beryl

The unification came in 1798, in Paris. The French crystallographer René Just Haüy had noticed that emerald and beryl crystals were geometrically identical, and asked the chemist Louis-Nicolas Vauquelin to analyse them. In a paper read that year before the Institut de France, Vauquelin reported a new "earth" extracted from emerald and beryl. The earth was the oxide of a previously unknown element — the metal we now call beryllium, named for the mineral that gave it up. Vauquelin's element stayed an oxide for another thirty years. Friedrich Wöhler and Antoine Bussy independently isolated metallic beryllium in 1828, by reacting potassium with beryllium chloride.

The named varieties

The 19th and early 20th centuries filled in the rest of the family. Aquamarine — the pale blue-green variety coloured by iron — kept its old Latin name (aqua marina, sea water). Heliodor, golden yellow, and goshenite, colourless, joined the list as colour-distinct varieties of the same species. Red beryl, the rarest of all, was first described in 1904 from Maynard's Claim in the Thomas Range of Juab County, Utah. The pink variety was named six years later, and named precisely. On 5 December 1910 the American gemmologist George F. Kunz proposed the name morganite at a meeting of the New York Academy of Sciences. The choice honoured the financier J. Pierpont Morgan for his support of the arts and sciences. Morgan had given important gem collections to the American Museum of Natural History in New York and to the Museum of Natural History in Paris; the pink colour itself comes from manganese.

Beryl is the world's principal ore of beryllium — a light, stiff, structural metal whose properties are so unusual that the small global supply finds its way into satellites, particle detectors, and the springs inside connector pins. Industrial use of beryl divides cleanly along that line: the mineral is mined either as a gemstone, where it stays beryl, or as feed for the beryllium industry, where it is broken down into the element and its compounds.

As an ore of beryllium

The most common alloy is beryllium copper, made by mixing about 2% beryllium into copper. The result is around six times stronger than copper alone, and — because it does not produce sparks when struck — it is shaped into hand tools used near flammable gases in refineries and on offshore rigs. The same alloy makes precision springs in electrical connectors and the strike-plates of percussion instruments.

Pure beryllium metal is far more specialised. Its low atomic number makes it almost transparent to X-rays. That property has driven the oldest and still one of the largest uses of the metal: the thin windows of X-ray tubes are routinely made of beryllium. In nuclear reactors the same element serves as a neutron reflector and neutron moderator — a material that bounces and slows neutrons so the chain reaction stays going.

Beryllium is also a structural material for precision optics. Its high elastic stiffness means a mirror or gyroscope made of beryllium flexes less under load than one made of any common alternative. The metal is now standard in inertial guidance systems and in the support mechanisms for optical instruments. The eighteen hexagonal mirror segments of the James Webb Space Telescope are machined from beryllium and plated with a thin layer of gold. Beryllium was chosen because it contracts and deforms less than glass at the telescope's 33 K operating temperature. The United States is one of only three countries that process beryllium ores and concentrates into beryllium products, and it supplies most of the rest of the world.

The use comes with a hazard. Beryllium-containing dust, inhaled, can cause berylliosis — a chronic, sometimes fatal allergic lung disease. The lung tissue scars with granulomas; in severe cases the disease leads to right-sided heart failure. Commercial production therefore runs under tight dust-control and industrial-hygiene regulation at every step from ore to finished part.

As a gemstone

Beryl's other industry is gem cutting. The species is the host of several of the most valuable coloured stones on Earth: emerald, green from traces of chromium and vanadium; aquamarine, blue-green from iron; morganite, pink from manganese; heliodor, golden yellow; and goshenite, colourless. Each is mined, cut and traded as its own gem variety rather than as "beryl", but the underlying crystal is the same beryllium-aluminium ring silicate in every case.