50 Fun Facts About Quartz

Quartz is composed of which compound?

Its atoms form a continuous framework of silicon-oxygen tetrahedra, each oxygen shared between two of them.

Quartz defines which value on the Mohs scale of hardness?

Topaz sits at 8 and orthoclase feldspar at 6; the scale was introduced by Friedrich Mohs in 1812.

By mass, quartz makes up about what share of the Earth's lithosphere?

Only the feldspar group, at 41%, is more abundant; pyroxenes come third at 11%.

The Ancient Greeks called quartz krystallos, meaning icy cold, because they believed it was what?

Pliny the Elder argued the case by noting it turned up near Alpine glaciers but not in hot countries; the idea lasted into the 17th century.

The word quartz, via German Quarz, is thought to come from a Polish dialect word meaning what?

The term kwardy matches the Czech tvrdy; another theory points to a Saxon word for cross-vein ore.

Whose 17th-century study of quartz established that its prism faces always meet at 60 degrees?

The law of constancy of interfacial angles holds whatever the crystal's size or shape.

At what temperature does normal alpha-quartz abruptly transform into high-temperature beta-quartz?

The volume change at that point can microfracture ceramics in a kiln or rocks after a fire.

The ideal quartz crystal is a prism with how many sides?

Each end terminates in a six-sided pyramid; crystals usually grow attached at one end so only one point shows.

The largest documented single quartz crystal, weighing over 39,900 kg, was found in which country?

It measured about 6.1 by 1.5 by 1.5 metres and came from near Itapore in Goias.

Which brothers discovered the piezoelectric properties of quartz in 1880?

Jacques and Pierre tested tourmaline, topaz, cane sugar and Rochelle salt too; quartz and Rochelle salt performed best.

The word piezoelectricity means electricity resulting from what?

It comes from the Greek piezo, to squeeze or press; gas lighters and stove igniters use the effect to make a spark.

The first quartz clock was built in 1927 by Warren Marrison and Joseph Horton at which laboratory?

It used a block of crystal pulsing 50,000 times a second, and proved more accurate than the best pendulum clocks.

At what frequency does the quartz crystal in nearly all modern quartz watches vibrate?

That is 2 to the power of 15, just above human hearing and easy to divide down to a one-second pulse; the crystal is cut as a tiny tuning fork.

The world's first commercial quartz wristwatch, the Astron of December 1969, was made by which company?

It was accurate to about a minute a year; the Swiss Beta 21 followed less than a year later.

The quartz crystal oscillator, key to radios and clocks, was first developed in 1921 by which physicist?

Pierce designed and patented his own oscillator circuits two years later.

Before World War II, which country was the sole source of electronics-grade quartz?

The wartime supply disruption drove the push for synthetic quartz, which now supplies virtually all industrial demand.

The Spruce Pine Mining District, a major source of ultra-pure quartz for silicon wafers, is in which US state?

High-purity quartz is defined as having under 50 parts per million of impurities.

What is the purple variety of quartz called?

The colour comes from iron impurities and natural irradiation, and it is February's birthstone.

The name of the purple quartz comes from Greek words meaning what?

The Greeks carved drinking cups from it in the belief that it would keep them sober; Anglican bishops still wear it in their rings.

The purple quartz was a cardinal gem until deposits in which country crashed its value?

The other four cardinal gems were diamond, sapphire, ruby and emerald.

Most commercially sold citrine, the yellow gem, is actually produced how?

Natural citrine is rare; the heat oxidises the iron that gives amethyst its purple.

The two-tone purple and yellow quartz called ametrine is mined almost entirely in which country?

The trade name bolivianite gives it away; the yellow zones were oxidised by heat while the purple ones were not.

The pink of massive rose quartz comes from fibrous inclusions related to which mineral?

A rarer form, pink quartz, grows as proper crystals but fades in light.

Smoky quartz's brown colour comes from radiation acting on colour centres around which impurity?

The very dark variety morion takes its name from a misreading of Pliny; Cairngorm is Scotland's local variety.

Cairngorm quartz, a smoky variety, is named after mountains in which country?

It has long been used in Scottish jewellery and dirk hilts.

Where was rare natural prasiolite, the green quartz, first found in the early 19th century?

The commercial stuff is made by heating amethyst to 400-500 C or irradiating yellow-tinged quartz.

The microcrystalline forms of quartz, such as agate and carnelian, are grouped together under what name?

Strictly it is a fine intergrowth of quartz with its monoclinic cousin moganite, and the name probably comes from the town of Chalcedon.

According to Theophrastus and Pliny, agate was named after a river on which island?

Etymologists suspect the River Achates was actually named after the stone.

Which German agate-cutting town later imported Brazilian agate as ship's ballast?

Its workshops developed the classic agate-dyeing methods and probably carved the so-called Aztec crystal skulls.

The name onyx comes from a Greek word meaning what?

Pink-and-white banded onyx can look like a nail, and the English word nail is a cognate.

The silky, shifting sheen of tiger's eye is described by what term?

It comes from parallel quartz crystals intergrown with altered amphibole fibres, and stones are cut as cabochons to show it off.

The common red colour of jasper is due to inclusions of what?

The jasper of antiquity was often green and translucent, and could include what we now call nephrite.

Flint, the quartz variety that defined the Stone Age, is a form of chert found in which rock?

It occurs as nodules in chalk and marly limestone, and struck against steel it throws sparks, hence the flintlock.

The shimmering quartzite aventurine takes its name from an Italian phrase meaning what?

The name first belonged to goldstone glass, said to have been made when a Murano workman spilled copper filings into the melt.

Herkimer diamonds, prized double-terminated quartz crystals, are found in dolomite in which US state?

Workmen cutting into the Mohawk Valley rock in the late 18th century turned them up in quantity.

Rhinestones were originally rock crystals gathered from which river?

Since the 19th century the name has meant lead glass; the Alsatian jeweller Georg Friedrich Strass perfected the metal-backed imitation diamond in the 1700s.

British Museum research showed its 'Aztec' crystal skull was carved with what, proving a 19th-century origin?

The skulls were most likely made in Idar-Oberstein from Brazilian quartz and sold through the Paris dealer Eugene Boban.

The Mitchell-Hedges crystal skull was allegedly found in 1924 at Lubaantun, in what is now which country?

Unlike the museum skulls it has a separate, movable lower jaw.

Shocked quartz, with microscopic planar deformation features, was first found after what?

Eugene Shoemaker then found it in impact craters such as Barringer and Chicxulub, and it backs the asteroid theory of the dinosaurs' end.

The dense silica polymorph coesite was first found in nature in 1960 at which Arizona site?

Its presence proved the crater was made by an impact; a still denser form, stishovite, turned up there in 1962.

Lechatelierite, an amorphous silica glass, is formed when what strikes quartz sand?

The glassy tubes left behind are called fulgurites.

Which German geologist first synthesised quartz in a sealed cooking vessel in 1845?

Nacken achieved commercial-scale synthesis a century later, and by the 1950s hydrothermal autoclaves were producing crystals industrially.

Quartzite is a hard metamorphic rock formed from which original rock?

The British Geological Survey requires at least 80% quartz by volume for the name.

Quartz is the mystical substance called maban in whose mythology?

It also turns up in European passage tombs such as Newgrange, and was knapped into tools in prehistoric Ireland.

Breathing fine crystalline silica dust from cutting quartz-bearing stone can cause which lung disease?

Respirable crystalline silica is a recognised human carcinogen as well.

Which mineral group is the only one more abundant than quartz in the Earth's lithosphere?

Feldspars make up about 41% of the lithosphere by mass, with pyroxenes just behind quartz at 11%.

Pliny the Elder argued quartz was permanently frozen ice because it was found where?

He noted it never appeared in warm climates, and the idea survived until at least the 17th century.

In which crystal system does ordinary low-temperature alpha-quartz crystallise?

Its high-temperature beta form has greater symmetry and belongs to the hexagonal system instead.

What is the name for a layer of well-formed crystals lining a cavity, of which quartz geodes are fine examples?

Such crystals are attached at one end to the rock, so only one termination pyramid forms; doubly terminated crystals grow free in gypsum.

Which German mineralogist had some success growing synthetic quartz in the 1930s and 1940s as war cut Brazilian supply?

Today almost all industrial quartz crystal comes from synthetic material grown by the hydrothermal process.