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50 free Quartz trivia questions with answers — nature quiz, new questions added Aug 2026.
Quartz is the second most common mineral in the Earth's crust, the reference point for a 7 on the Mohs scale, and the reason your watch keeps time. This quiz starts with the mineral itself: silicon dioxide, the six-sided crystals, the alpha-beta flip at 573 degrees, why the Greeks called it krystallos and thought it was permanent ice, and Nicolas Steno's 60-degree angles that founded crystallography. The middle of the quiz is the coloured family. Amethyst and the drunkenness it was meant to prevent, citrine cooked from amethyst, rose quartz, smoky quartz and Scotland's Cairngorm, Bolivia's two-tone ametrine, banded agate and onyx, tiger's eye, red jasper, flint and the Stone Age. Then comes the technology: the Curie brothers discovering piezoelectricity in 1880, the first quartz clock at Bell Labs in 1927, the 32,768 Hz tuning fork inside almost every watch, and the Seiko Astron of Christmas 1969. It ends with the oddities: Herkimer diamonds, rhinestones from the Rhine, 19th-century crystal skulls sold as Aztec, shocked quartz from nuclear tests and impact craters, and a 40-tonne Brazilian crystal. Easy questions suit anyone who owns a quartz watch; the expert tier is for geology students and rockhounds. Every answer was checked against Wikipedia's articles on quartz, its varieties and its uses, and the supporting sentence is attached to each question.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Quartz is composed of which compound?
Silicon dioxide
Its atoms form a continuous framework of silicon-oxygen tetrahedra, each oxygen shared between two of them.
Q 02Quartz defines which value on the Mohs scale of hardness?
7
Topaz sits at 8 and orthoclase feldspar at 6; the scale was introduced by Friedrich Mohs in 1812.
Q 03By mass, quartz makes up about what share of the Earth's lithosphere?
12%
Only the feldspar group, at 41%, is more abundant; pyroxenes come third at 11%.
Q 04The Ancient Greeks called quartz krystallos, meaning icy cold, because they believed it was what?
Supercooled ice
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.
Q 05The word quartz, via German Quarz, is thought to come from a Polish dialect word meaning what?
Hard
The term kwardy matches the Czech tvrdy; another theory points to a Saxon word for cross-vein ore.
Q 06Whose 17th-century study of quartz established that its prism faces always meet at 60 degrees?
Nicolas Steno
The law of constancy of interfacial angles holds whatever the crystal's size or shape.
Q 07At what temperature does normal alpha-quartz abruptly transform into high-temperature beta-quartz?
573 C
The volume change at that point can microfracture ceramics in a kiln or rocks after a fire.
Q 08The ideal quartz crystal is a prism with how many sides?
Six
Each end terminates in a six-sided pyramid; crystals usually grow attached at one end so only one point shows.
Q 09The largest documented single quartz crystal, weighing over 39,900 kg, was found in which country?
Brazil
It measured about 6.1 by 1.5 by 1.5 metres and came from near Itapore in Goias.
Q 10Which brothers discovered the piezoelectric properties of quartz in 1880?
The Curies
Jacques and Pierre tested tourmaline, topaz, cane sugar and Rochelle salt too; quartz and Rochelle salt performed best.
Q 11The word piezoelectricity means electricity resulting from what?
Pressure
It comes from the Greek piezo, to squeeze or press; gas lighters and stove igniters use the effect to make a spark.
Q 12The first quartz clock was built in 1927 by Warren Marrison and Joseph Horton at which laboratory?
Bell Telephone Laboratories
It used a block of crystal pulsing 50,000 times a second, and proved more accurate than the best pendulum clocks.
Q 13At what frequency does the quartz crystal in nearly all modern quartz watches vibrate?
32,768 Hz
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.
Q 21Most commercially sold citrine, the yellow gem, is actually produced how?
Heating amethyst or smoky quartz
Natural citrine is rare; the heat oxidises the iron that gives amethyst its purple.
Q 22The two-tone purple and yellow quartz called ametrine is mined almost entirely in which country?
Bolivia
The trade name bolivianite gives it away; the yellow zones were oxidised by heat while the purple ones were not.
Q 23The pink of massive rose quartz comes from fibrous inclusions related to which mineral?
Dumortierite
A rarer form, pink quartz, grows as proper crystals but fades in light.
Q 14The world's first commercial quartz wristwatch, the Astron of December 1969, was made by which company?
Seiko
It was accurate to about a minute a year; the Swiss Beta 21 followed less than a year later.
Q 15The quartz crystal oscillator, key to radios and clocks, was first developed in 1921 by which physicist?
Walter Guyton Cady
Pierce designed and patented his own oscillator circuits two years later.
Q 16Before World War II, which country was the sole source of electronics-grade quartz?
Brazil
The wartime supply disruption drove the push for synthetic quartz, which now supplies virtually all industrial demand.
Q 17The Spruce Pine Mining District, a major source of ultra-pure quartz for silicon wafers, is in which US state?
North Carolina
High-purity quartz is defined as having under 50 parts per million of impurities.
Q 18What is the purple variety of quartz called?
Amethyst
The colour comes from iron impurities and natural irradiation, and it is February's birthstone.
Q 19The name of the purple quartz comes from Greek words meaning what?
Not intoxicated
The Greeks carved drinking cups from it in the belief that it would keep them sober; Anglican bishops still wear it in their rings.
Q 20The purple quartz was a cardinal gem until deposits in which country crashed its value?
Brazil
The other four cardinal gems were diamond, sapphire, ruby and emerald.
Q 24Smoky quartz's brown colour comes from radiation acting on colour centres around which impurity?
Aluminium
The very dark variety morion takes its name from a misreading of Pliny; Cairngorm is Scotland's local variety.
Q 25Cairngorm quartz, a smoky variety, is named after mountains in which country?
Scotland
It has long been used in Scottish jewellery and dirk hilts.
Q 26Where was rare natural prasiolite, the green quartz, first found in the early 19th century?
Lower Silesia, Poland
The commercial stuff is made by heating amethyst to 400-500 C or irradiating yellow-tinged quartz.
Q 27The microcrystalline forms of quartz, such as agate and carnelian, are grouped together under what name?
Chalcedony
Strictly it is a fine intergrowth of quartz with its monoclinic cousin moganite, and the name probably comes from the town of Chalcedon.
Q 28According to Theophrastus and Pliny, agate was named after a river on which island?
Sicily
Etymologists suspect the River Achates was actually named after the stone.
Q 29Which German agate-cutting town later imported Brazilian agate as ship's ballast?
Idar-Oberstein
Its workshops developed the classic agate-dyeing methods and probably carved the so-called Aztec crystal skulls.
Q 30The name onyx comes from a Greek word meaning what?
Fingernail
Pink-and-white banded onyx can look like a nail, and the English word nail is a cognate.