40 Fun Facts About Graphite

Graphite was once mistaken for an ore of which metal, the mix-up that gave pencil cores their name?

Lead ores such as galena look much like graphite, so miners named the mineral after the metal. No pencil core has ever contained any.

At room temperature, graphite is more stable than which gemstone made of the same atoms?

Diamond is only metastable at the Earth's surface and is, in theory, turning into graphite, though far too slowly for anyone to notice.

Before pencils existed, what did locals in England's Borrowdale valley first use graphite for?

Marking sheep was the first job for the soft black mineral found near Seathwaite in the 1500s. The deposit was so pure it could be sawn straight into rods.

England's Crown guarded a Borrowdale graphite mine because the mineral lined the moulds for what?

Cannonballs made in graphite-lined moulds came out rounder and smoother, so they flew farther. That made one small mine a military asset.

Two physicists won a Nobel Prize after peeling atom-thin flakes off graphite with which office item?

Adhesive tape pulled ever-thinner flakes off a lump of graphite until a single layer was left. Andre Geim and Konstantin Novoselov shared the 2010 physics prize.

The first nuclear reactor, a pile of graphite blocks, ran in 1942 under a stadium in which US city?

Chicago hosted the pile in an old rackets court under the stands of Stagg Field, where the university had dropped football three years earlier.

Graphite forms the negative electrode in which battery type, first sold by Sony in 1991?

Lithium-ion cells rely on graphite because ions can slip between its layers and out again without wrecking it. One electric car pack can hold nearly 40 kg of the mineral.

Graphite bombs, dropped on Yugoslavia in 1999, scatter fine filaments designed to knock out what?

Power grids short out when the threads settle across lines and transformers. One 1999 strike cut more than 70% of the national supply, though it was restored within a day.

A thin slice of pyrolytic graphite will do what above strong magnets, with no batteries or cooling?

Levitate is exactly what it does: pyrolytic graphite repels magnetic fields more strongly, weight for weight, than any other room-temperature material.

Graphite grains older than the Solar System, forged around dying stars, have turned up inside what?

Meteorites carry graphite specks whose odd isotope mix shows they formed around other stars, making graphite one of about a dozen minerals known to predate the Sun.

Graphite is a crystalline form of which chemical element, number six on the periodic table?

Carbon atoms in graphite sit in flat sheets that slide over each other, which is why the mineral feels slippery and rubs off on paper.

What name is given to a single atom-thick sheet of graphite, hailed as a wonder material since 2004?

Graphene is one sheet of atoms, and graphite is simply a stack of them. A square-metre hammock of it could, in theory, hold a 4 kg cat yet weigh about as much as one whisker.

Graphite's name, coined by a German mineralogist in 1789, comes from a Greek verb meaning what?

To write or draw is the sense of the Greek graphein, chosen because the mineral leaves marks on paper. The new name replaced labels that wrongly tied it to a metal.

Modern pencil cores follow a 1795 French recipe that bakes powdered graphite with which material?

Clay sets the grade: the more of it in the mix, the harder and paler the line. That ratio is what separates a 2H from a 2B.

Powdered graphite is puffed into stiff locks because the mineral works as a dry what?

Lubricant is one of graphite's main jobs because its flat sheets slide over one another. It is the pick for machines that run very hot or very cold.

Cub Scouts dust graphite powder onto the axles of their model cars before which racing event?

Pinewood derby racers polish the nail axles and add graphite to cut friction. The first race was run in California in 1953, and Scouting adopted it within a year.

Huge graphite electrodes carry the current in arc furnaces that melt scrap into which metal?

Steel made from scrap this way relies on graphite electrodes that can be 3.5 metres long and 75 cm across, baked at close to 3,000 °C.

Red-hot graphite blocks were blasted out of the reactor core during which 1986 nuclear disaster?

Chernobyl's reactor used graphite to keep its chain reaction going, and about a quarter of the blocks were thrown out by the blast. Much of the rest burned for days.

Which writer, famed for a book about life by a pond, worked in the family graphite pencil factory?

Henry David Thoreau kept working at the family factory for most of his adult life, and worked out how to make good pencils from inferior local graphite.

Which sport's players use 'graphite' shafts, some under 50 grams, because lighter ones swing faster?

Golf moved from hickory shafts to metal and then to graphite, which is really a fibre composite. The lighter shaft lets a club be swung at greater speed.

Graphite blocks fill the core of some nuclear reactors in order to slow down which particles?

Neutrons bounce off graphite's light atoms and lose speed, which makes them far more likely to split the next uranium atom and keep the chain reaction going.

Which physicist led the team that stacked graphite blocks into the first nuclear reactor in 1942?

Enrico Fermi described his creation as little more than a heap of black bricks and timber. His safety sums were trusted enough to run it in the middle of a crowded city.

Britain's worst nuclear accident began in 1957 when a graphite reactor overheated at which site?

Windscale's operators were heating the core on purpose, to release energy that builds up in irradiated graphite, when it caught alight. The site is now called Sellafield.

The US Air Force banned graphite powder on its aircraft because, when damp, it corrodes which metal?

Aluminum is vulnerable enough that even a graphite pencil mark left on a part can help corrosion take hold.

Graphite became a key ingredient of heavy-vehicle brake linings as a substitute for which mineral?

Asbestos once did the job; when it had to be replaced, fine flake graphite took its place in the brake shoes of heavier vehicles.

Flakes of graphite scattered through which metal give its broken surfaces a grey colour?

Cast iron of the grey kind is 6 to 10% graphite by volume, and the flakes soak up vibration, which is why it makes good bases for machine tools.

Which old name for graphite, kept for 17th- and 18th-century portrait drawings, is also a genus of flowering plants?

Plumbago was what artists called a raw lump of the mineral used for drawing with no wooden casing, which is how the portraits got their label.

Atoms in each sheet of graphite bond into a flat net of which repeating shape, like chicken wire?

Hexagons give every atom three close neighbours, just 0.142 nanometres away, in a pattern often compared to honeycomb.

Graphite went into the radar-absorbing tiles of which American stealth jet, first flown in 1981?

F-117 Nighthawk tiles were not graphite's first stealth job: German U-boats had already worn it, mixed with rubber, on their snorkels to hide from radar.

Graphite-fibre composites form the fuselage of which airliner, which entered service in 2011?

Boeing 787 Dreamliners were the first airliners with a mostly composite airframe, their fuselage built as one-piece barrels instead of sheets joined by many fasteners.

Which German geologist, whose pupils at Freiberg included Friedrich Mohs, named graphite in 1789?

Abraham Gottlob Werner wanted to end a muddle of old names, after tests had shown that three look-alike soft black minerals were in fact different substances.

Edward Acheson built his synthetic graphite works beside which waterfall, drawn by cheap energy?

Niagara Falls supplied the current his hungry furnaces needed. He had hit on the method by accident, overheating an abrasive he invented until only graphite was left.

Which island, then a British colony, supplied about a third of the world's graphite in 1899?

Sri Lanka's graphite is the rare vein kind, pure enough to dig out in lumps, and it has been known since a Dutch governor wrote about it in 1675.

Graphite's sheets slide apart so easily because they are held to one another only by what?

Van der Waals forces between the sheets are feeble next to the bonds inside each one, so a pencil sheds flakes at the lightest touch.

In the fourth millennium BC, people in south-eastern Europe used graphite paint to decorate what?

Pottery of the Marița culture carried graphite paint thousands of years before anyone thought of drawing on paper with the mineral.

Heated without air at normal pressure, graphite never melts; at about 3,600 °C it does what instead?

Turns to vapour is all it can do, because its liquid form exists only above about 100 atmospheres. No other element sublimes at a higher temperature.

Strips of expandable graphite swell when heated to seal the gaps around which building fixtures?

Fire doors rely on graphite that expands and chars when hot, blocking smoke and flame. The same trick is used in metal collars fitted around plastic pipes.

A graphite block absorbs spent proton beams in the 'beam dump' of which 27-kilometre accelerator?

Large Hadron Collider beams pack the energy of about 87 kg of TNT, so each one is steered into a graphite absorber when it is no longer wanted.

Glassworkers use graphite tools because, unlike bare metal, graphite will not do what to hot glass?

Stick to it is what bare metal does, so metal tools and moulds need a coating first, and that coating is often graphite-based too.

Grains of smokeless gunpowder are coated in graphite to prevent a dangerous build-up of what?

Static charge drains away through the graphite coat, so a stray spark cannot set the grains off. The glaze also helps the powder flow when it is blended.