49 Fun Facts About Crystal

The word crystal comes from the Ancient Greek krustallos, which meant both 'rock crystal' and what?

Greek philosophers including Theophrastus thought quartz was supercooled ice, an idea Pliny the Elder repeated and which lasted into the 17th century.

Despite the name, lead crystal and crystal glass are actually what kind of solid?

Lead crystal and crystal glass are amorphous solids: their atoms have no long-range periodic order, so 'crystal' glassware is named for its sparkle and clarity, not its structure.

Crystal structures are grouped into how many crystal systems?

Crystallographers recognise seven crystal systems, defined by the symmetry of the unit cell; the 14 Bravais lattices and 32 point groups sort into them.

Which symmetry can quasicrystals show that is impossible for an ordinary periodic crystal?

Quasicrystals show five-fold (and ten-fold) rotational symmetry, forbidden for periodic lattices; a holmium-magnesium-zinc quasicrystal even grows as a pentagonal dodecahedron, and the IUCr redefined 'crystal' in 1992.

Quartz defines which value on the Mohs hardness scale?

Quartz is the reference mineral for 7 on the Mohs scale, between orthoclase feldspar at 6 and topaz at 8; it scratches ordinary window glass and a steel knife blade.

Whose 17th-century study of quartz paved the way for modern crystallography?

Nicolas Steno showed in 1669 that quartz crystals keep the same angles between corresponding faces whatever their size or shape, the law of constant interfacial angles.

Amethyst gets its name from a Greek word meaning what?

Ancient Greeks carved drinking vessels from it believing it prevented drunkenness; the violet colour comes from irradiated iron impurities.

The Cave of the Crystals near Naica, Mexico, holds giant crystals of which mineral?

The Naica crystals are selenite gypsum, the transparent crystalline form of the mineral; the largest is about 11.4 metres long, and the chamber sits at 58°C with humidity near 99%.

Who discovered the Cave of the Crystals in April 2000?

Two brothers drilling in the mine, Juan and Pedro Sánchez, broke into the chamber in April 2000 while cutting a new tunnel at Naica; when the mine's pumps were later switched off the chamber reflooded.

Roughly how long did the Naica crystals take to grow to their enormous size?

Fluid-inclusion studies indicate growth took at least 500,000 years, as mineral-rich water held just below 58°C let gypsum crystallise at an extremely slow rate.

A snowflake's six-fold symmetry comes from what?

The hexagonal crystal structure of ice (ice Ih) sets the 60-degree angles between a snow crystal's arms; rare twelve-branched flakes are two such crystals grown together.

Guinness lists the largest snowflakes, 15 inches wide, as falling in 1887 at Fort Keogh in which state?

Fort Keogh, near Miles City in Montana, reported flakes 15 inches wide and 8 inches thick on 28 January 1887; typical aggregate flakes are no more than 3 or 4 inches across.

Wilson 'Snowflake' Bentley photographed his first snowflake in 1885 on his family farm in which state?

Bentley, a farmer in Jericho, Vermont, caught flakes on black velvet and coupled a bellows camera to a microscope; his 1885 photomicrograph is considered the first of a single snow crystal.

Which physicist won the 1914 Nobel Prize for showing that crystals diffract X-rays?

Max von Laue conceived the experiment in 1912 after a conversation with Paul Ewald in Munich; Friedrich and Knipping shot the first diffraction pattern through a copper sulfate crystal.

Which father-and-son pair shared the 1915 Nobel Prize in Physics for their crystallography work?

The father-and-son Braggs shared the 1915 prize; the son's Bragg's law relates X-ray wavelength and angle to the spacing of atomic planes, and at 25 he became the youngest physics laureate.

What was the first crystal structure solved to atomic resolution, in 1914?

Table salt (sodium chloride) was the first structure solved by X-ray diffraction, a lattice of alternating sodium and chloride ions with no discrete molecules; copper, fluorite, calcite and pyrite followed.

The United Nations proclaimed which year the International Year of Crystallography?

The UN General Assembly designated 2014 the International Year of Crystallography in July 2012, marking a century since the 1912 discovery that crystals diffract X-rays.

Which French siblings discovered piezoelectricity in 1880 using crystals such as quartz and tourmaline?

The Curies, brothers Pierre and Jacques, found in 1880 that pressing quartz, tourmaline or Rochelle salt produced a voltage; Rochelle salt gave the strongest effect, and piezoelectric igniters spark gas lighters.

At what frequency does the tuning-fork quartz crystal in nearly all quartz timepieces vibrate?

The crystal vibrates at 32,768 Hz, which is 2 to the 15th power, so a chain of 15 binary dividers yields exactly one pulse per second; Seiko's Astron of 1969 was the first quartz wristwatch.

Where was the first quartz clock built in 1927?

Warren Marrison and J. W. Horton built the first quartz clock at Bell Labs (Bell Telephone Laboratories) in 1927, using a crystal oscillator as a frequency standard for the telephone network.

Under EU rules, glass may only be labelled 'lead crystal' if it contains at least how much lead oxide?

EU Directive 69/493/EEC reserves 'lead crystal' for glass with at least 24% lead oxide and 'full lead crystal' for 30% or more; lighter mixes are sold as 'crystal glass' or 'crystallin'.

Swarovski built its crystal-cutting factory in which Austrian town for hydroelectric power?

Daniel Swarovski, a Bohemian-born glass cutter, set up in Wattens in the Tyrol in 1895 because local hydroelectric power could drive his patented electric cutting machine; the Kristallwelten museum opened there in 1995.

Crystal-making in Waterford, Ireland dates back to 1783 and which pair of founders?

That original glassworks shut in 1851; the modern company's main plant closed in 2009 and the brand now belongs to Fiskars.

Which magazine's quip gave Joseph Paxton's 1851 Great Exhibition hall the nickname Crystal Palace?

Punch's Douglas Jerrold called Paxton's glass hall 'a palace of very crystal', and the nickname Crystal Palace stuck; the building moved to Sydenham in 1854 and burned down in November 1936.

Rotary jeweller's tool marks on the British Museum's crystal skull date it to which century?

Electron microscopy of the British Museum skull found grooves cut with a rotary wheel, a tool unknown in pre-Columbian Mesoamerica, so it was carved in the 19th century; it came via Paris dealer Eugène Boban.

Which Elizabethan mathematician and consultant to Queen Elizabeth I is famous for scrying with crystals?

John Dee, Elizabeth I's astrologer and mathematician, used a crystal ball and an obsidian mirror with his medium Edward Kelley to 'converse with angels'; both objects ended up in the British Museum.

What does scientific research say about crystal healing?

Christopher French's experiments with real and fake quartz found the same reported sensations whichever crystals volunteers held, so its effects match a placebo; crystal healing is classed as pseudoscience.

Diamond crystallises in which crystal system?

Diamond belongs to the cubic system: each carbon atom bonds tetrahedrally to four others in a face-centred cubic lattice, and its crystals typically grow as octahedra.

Most natural diamonds are how old?

Most natural diamonds formed 1 to 3.5 billion years ago at depths of 150 to 250 kilometres, reaching the surface much later in kimberlite and lamproite eruptions.

The Cullinan, the largest gem-quality rough diamond ever found, weighed how many carats?

The Cullinan, 3,106 carats (about 621 grams), was found at the Premier Mine near Pretoria in January 1905 and cut in Amsterdam by Joseph Asscher & Co. into nine major stones.

Herkimer 'diamonds', found in dolomite in New York's Mohawk Valley, are actually what?

Herkimer diamonds are double-terminated quartz crystals, pointed at both ends because they grew unattached inside cavities in dolomite; they are also called Middleville or Little Falls diamonds.

Halite, or rock salt, forms crystals of which shape?

Halite grows as cubes because its sodium and chloride ions alternate in a simple three-dimensional lattice; it cleaves perfectly along three perpendicular directions and has a Mohs hardness of 2 to 2.5.

The rainbow colours on lab-grown bismuth 'hopper' crystals come from what?

The colours are thin-film interference in an oxide layer of bismuth whose thickness varies across the surface; the stair-step hopper shape forms because crystal edges grow faster than the faces.

Rock candy is made by letting a supersaturated sugar solution crystallise onto what?

A supersaturated syrup is left to cool with a string or stick suspended in it; sugar crystallises onto that seed over several days, and in Iran the result is called nabat.

Which Austrian botanist discovered liquid crystals in 1888 while studying cholesterol from carrots?

Friedrich Reinitzer, working in Prague, found in 1888 that cholesteryl benzoate had two melting points, turning cloudy at 145.5°C and clear at 178.5°C; physicist Otto Lehmann then named the state liquid crystal.

Large amethyst-lined geodes are a feature of the basalts of which two South American countries?

Brazil and Uruguay, especially Rio Grande do Sul and the Artigas department, yield the huge amethyst geodes, formed in gas cavities of the Paraná flood basalts; some 'cathedral' geodes stand taller than a person.

Roughly what share of snowflakes actually show the ideal six-fold symmetric shape?

Less than 0.1% of snowflakes show the textbook symmetric form; most are irregular, clumped or broken, and Ukichiro Nakaya's morphology diagram links each crystal type to the temperature and humidity it grew in.

Diamond's name derives from a Greek word meaning what?

Diamond comes from the Greek adamas, 'unbreakable' or 'untameable', from a- ('not') and daman ('to tame'); the same root gave English 'adamant'.

Above what temperature does ordinary alpha-quartz abruptly turn into beta-quartz?

The alpha-to-beta inversion happens at 573°C at atmospheric pressure and reverses on cooling, so every quartz crystal at room temperature is alpha-quartz; the change is used as a marker in ceramics firing.

Which of the British crown jewels holds Cullinan I, the 530-carat Great Star of Africa?

Cullinan I was set in the head of the Sovereign's Sceptre with Cross in 1910 for George V; Cullinan II, the 317-carat Second Star of Africa, sits in the Imperial State Crown.

Which scientist argued in 1907 that X-rays were not electromagnetic radiation?

William Henry Bragg held in 1907 that X-rays were streams of neutral particles, sparring with Charles Barkla, who showed their polarisation; Bragg later accepted the wave picture and used it for diffraction.

Which mineral forms the world's largest known natural crystal, 18 m long in Madagascar?

The Malakialina beryl, found in a pegmatite in Madagascar, measures 18 m long and 3.5 m across and weighs about 380 tonnes, roughly a fully loaded jumbo jet.

Which impurity turns a diamond crystal slightly blue?

Boron atoms substituting for carbon absorb red light, giving Type IIb diamonds like the Hope a blue tint; nitrogen, the commonest impurity, yellows a stone instead.

Who received the 2011 Nobel Prize in Chemistry for discovering quasicrystals?

Dan Shechtman saw ten-fold diffraction symmetry in a rapidly cooled aluminium-manganese alloy on 8 April 1982; ridiculed for years, he won the 2011 chemistry Nobel alone.

Chocolate can crystallise into how many different forms, only one of which suits candy bars?

Cocoa butter has six polymorphs, numbered I to VI; tempering coaxes it into form V, which gives the glossy finish, clean snap and a melting point just below body temperature.

Which industrial technique grows large single-crystal boules, notably silicon for chips?

In the Czochralski process a seed crystal is dipped into molten silicon and slowly pulled upward while rotating, drawing out a single-crystal boule that is sliced into wafers; Jan Czochralski discovered it in 1916.

What are crystals with obvious, well-formed flat faces called?

Euhedral crystals show sharp, well-developed faces because they grew with free space around them; anhedral grains lack faces, usually because they crystallised jammed against their neighbours.

The angular Widmanstätten patterns seen in iron meteorites result from what?

The pattern records extremely slow cooling in space, a few degrees per million years, inside the metal cores of shattered asteroids; kamacite and taenite separate into interleaved plates along octahedral planes.

Which optical property makes a double image appear when you look through a crystal such as calcite?

Birefringence splits light into two rays with different refractive indices along different crystal directions; a calcite rhomb laid on print shows every letter doubled, an effect Rasmus Bartholin described in 1669.