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Minerals

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The Mohs Scale
Named Stones
Other

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Minerals

The Mohs Scale

The Mohs scale of mineral hardness was created in 1812 by the German geologist and mineralogist Friedrich Mohs. It's often mistakenly referred to as Moh's Scale.

In a normal pub quiz, you're only likely to get asked what's number 1 (least hard) or number 10 (hardest). In the leagues, these are normally considered too easy and you're more likely to get asked what's number 2 or number 9. Some question setters seem to feel that once numbers 2 and 9 have been asked, numbers 3 and 8 are fair game. There is bound to come a time when you're expected to know all ten. I therefore make no apology for listing them all; but to make it fairer, I've included a description of each mineral.

1 A clay mineral composed of hydrated magnesium silicate; commonly used as an astringent powder Click to show or hide the answer
2 A soft sulfate mineral composed of calcium sulfate dihydrate; used as a fertilizer, and as the main constituent in many forms of plaster (including plaster of Paris), blackboard chalk and plasterboard Click to show or hide the answer
3 The most stable polymorph of calcium carbonate Click to show or hide the answer
4 The colourful mineral form of calcium fluoride Click to show or hide the answer
5 A group of phosphate minerals, often mistaken for other minerals; hence the name, which is derived from a Greek word meaning to deceive or to be misleading Click to show or hide the answer
6 One of a group of minerals that make up around 60% of the Earth's crust; the principal constituent of the gem known as moonstone; its name comes from the fact that it has two cleavage planes that are at right angles to each other Click to show or hide the answer
7 The second most abundant mineral in the earth's crust, being an oxide of silicon; it has many different varieties, several of which are semi–precious gemstones Click to show or hide the answer
8 A silicate mineral of aluminium and fluorine: colourless in its pure form, but usually tinted by impurities; traditionally the birthstone for November Click to show or hide the answer
9 A crystalline form of aluminium oxide: colourless when pure, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red and padparadscha if pink–orange; all other colors are called sapphire (the best–known being the green variety). Commonly used as an abrasive, e.g. in sandpaper Click to show or hide the answer
10 An allotrope of carbon, highly valued as a precious gemstone Click to show or hide the answer

Named Stones

The second largest gem diamond ever found in Russia or the Soviet Union: found in 1989 at a mine in north–eastern Siberia, and weighing 320.65 carats (64.130 g), it was named after a famous Russian writer and is kept in the Russian Diamond Fund (in the Kremlin) Click to show or hide the answer
Found in the Crater of Diamonds State Park, Arkansas, by holidaymaker W. W. Johnson in 1975, and named after his home town: when unearthed it weighed 16.37 carats (3.274 g), but it has since been cut into a 7.54 carat (1.508 g) marquise shape Click to show or hide the answer
The largest rough pink diamond ever unearthed in Australia: found in 2011 at Rio Tinto's Argyle diamond mine in Western Australia; originally weighing 12.76 carats (2.552 g), but found to have one major internal fault line; after cutting it was 8.01 carats (1.602 g) and was donated to the Melbourne Museum Click to show or hide the answer
Famous gem (actually a spinel) in the British Imperial State Crown; named after the son and heir of King Edward III, to whom it was given in 1467 by King Peter of Castile and Leon (Don Pedro – by whom it was said to have been stolen from the Moorish Prince of Granada) in return for his help in quelling a revolt led by Don Pedro's brother Henry Click to show or hide the answer
Found in 1932 by 12–year–old Roy Spencer, and used as a doorstop in his family's home for ten years: the world's largest gem quality "star" sapphire (now owned by an unknown private party) Click to show or hide the answer
Discovered in 1986 in South Africa, in the same mine as the Cullinan (since renamed the Cullinan Mine); 273.85 carats; displayed for several years in the Tower of London Click to show or hide the answer
Largest diamond ever found (South Africa, 1905) – cut into pieces, including the Great Star of Africa and the Second Star of Africa (a.k.a. Cullinan I and II) Click to show or hide the answer
Largest diamond ever found, prior to the Cullinan (S. Africa, 1893) Click to show or hide the answer
24.78–carat diamond, mounted in a ring, sold by Sotheby's in Geneva for £29 million in 2010 – the most expensive single jewel ever sold at auction, until displaced by the Pink Star Click to show or hide the answer
The world's largest diamond (546 carats – 15 carats more than the Cullinan) – discovered in South Africa in 1985; bought in 1995 by the Burmese–born, Thai–based jewellery dealer Henry Ho Click to show or hide the answer
27.64–carat diamond, of an extremely rare blue colour, found in South Africa (in the same mine as the Cullinan and the Centenary) and unveiled in 2000: rumoured in 2012 to have been bought by the boxer Floyd Mayweather Jr. for his fiancée, Shantel Jackson Click to show or hide the answer
Presented to Louis XIV by Jean Baptiste Tavernier and to Marie Antoinette by Louis XVI Click to show or hide the answer
Diamond named after its South African discoverer (1934) – 726 carats; sold in 1935 to a New York dealer for £150,000; cut into 13 pieces, the largest of which was 142.9 ct when finished Click to show or hide the answer
Once the largest known diamond – originated in India, became part of the British crown jewels 1877. Name means "mountain of light" Click to show or hide the answer
Discovered in Zaire in 1990, and bought by De Beers – 777 carats uncut; centrepiece of the exhibition at London's Millennium Dome, in 2000, that was the target of a foiled raid Click to show or hide the answer
The largest known red diamond (the rarest colour): discovered in Brazil in the 1990s; named after the Israeli–born, London–based jewellery dealer who bought it in 2001 or 2002 (previously known as the Red Shield) Click to show or hide the answer
Mined by De Beers in South Africa, 1999: 132.5 carat in the rough; previously known as the Steinmetz Pink; sold at auction in 2013 for £52 million, a world record for any gemstone; but the buyer (a New York diamond cutter, who chose to name it Pink Dream) couldn't raise the funds, and it remains in Sotheby's inventory Click to show or hide the answer
Alternative name for Cullinan I, the largest polished gem cut from the Cullinan diamond (530 carats) in the British royal sceptre. It was the world's largest diamond, until the discovery of the Golden Jubilee Diamond in 1985 Click to show or hide the answer
Mined in Sri Lanka, during Dutch or British colonisation, probably around 1700; now in the American Museum of Natural History, New York: the world's second largest "star" sapphire Click to show or hide the answer
Nickname of the largest diamond ever discovered in the USA: found in 1924 at the Prairie Creek pipe mine in Murfreesboro, Arkansas (which later became known as the Crater of Diamonds State Park), by Wesley Oley Basham, an employee of the Arkansas Diamond Corporation; originally weighed 40.23 carats (8.046 g); after cutting, 12.42 carats (2.484 g) Click to show or hide the answer

Other

The three types of gem that aren't minerals:

Fossilised resin from coniferous trees Click to show or hide the answer
Red or pink, made from the skeleton of a type of marine animal Click to show or hide the answer
Produced in the soft tissue of a living shelled mollusc Click to show or hide the answer

Snow–white variety of gypsum (calcium sulphate) – extracted in the English midlands since at least the 15th century Click to show or hide the answer
Violet variety of quartz, often used in jewellery: name comes from the Greek meaning 'not intoxicated' – a reference to the belief that the stone protected its owner from drunkenness Click to show or hide the answer
Considered rare and precious in the Old World – one of the five 'cardinal gems', along with diamond, emerald, ruby and sapphire – until large deposits were found in Brazil around 1900
High quality (hard, brittle, shiny) coal, over 90% carbon, mined in South Wales and used in steam engines Click to show or hide the answer
Named from a Greek word meaning "unquenchable" or "inextinguishable"; chrysolite, amosite, crocidolite (from a Greek term that can be translated as "woolly rock"), tremolite, anthophyllite and actinolite are the six types of Click to show or hide the answer
Rock that forms the hexagonal columns in the Giant's Causeway and Fingal's Cave (a common volcanic rock, formed by the rapid cooling of lava when it's exposed on or very near the Earth's surface) Click to show or hide the answer
First discovered at Les Baux in southern France Click to show or hide the answer
Highly absorbent type of clay, named in 1898 after a city in Montana: widely used in the oil, steel and construction industries, as well as in wine and beer making, as a laxative, and in cat litter Click to show or hide the answer
Aquamarine, emerald, morganite and heliodor are coloured varieties of (colourless when pure) Click to show or hide the answer
Medium–grade coal, about 60–80% carbon, named after the tar–like substance that it contains Click to show or hide the answer
Form of fluorspar (fluorite) found in the south Pennines – particularly in a famous cave near Castleton, Derbyshire; named for its blue and yellow staining Click for more information Click to show or hide the answer
Form of dolerite found in the Preseli hills of Pembrokeshire, extensively used in Stonehenge – named after the distinctive colour it appears when wet Click to show or hide the answer
Coal low in spores and algae, with no visible structure Click to show or hide the answer
The three Cs that determine the value of a diamond Click to show or hide the answer
Agate, Onyx, Sardonyx, and carnelian are all forms of Click to show or hide the answer
Sedimentary rock of which flint is a variety Click to show or hide the answer
Rocks that are rich in the clay mineral kaolinite are known as kaolin, or Click to show or hide the answer
Variety of quartz – rare in nature, but produced artificially by heating amethyst or other quartzes: name is from the Latin for 'yellow' Click to show or hide the answer
Saccharine is made from Click to show or hide the answer
Crystalline form of aluminium oxide, of which ruby and sapphire are forms Click to show or hide the answer
Precious stone that is a green variety of beryl Click to show or hide the answer
Mineral calcium fluoride; colourless when pure, otherwise violet, blue, yellow, brown, or green Click to show or hide the answer
Alternative name for iron pyrites or pyrite (mineral iron disulphide, FeS2) Click to show or hide the answer
Coarse–grained igneous crystalline rock: typically composed of quartz, feldspar and mica Click to show or hide the answer
Crystalline form of carbon, sometimes known as plumbago or black lead, from which pencil leads are made Click to show or hide the answer
Hard, coarse–grained, siliceous sandstone, characteristic of the Peak District and Pennines of Northern England; term especially applied to such sandstones that are quarried for building material, or for use as millstones; gives its name to a 35–mile walkers' trail across the Peak District, from Disley in Greater Manchester to Kidsgrove in Staffordshire Click to show or hide the answer
Mineral calcium sulphate from which plaster of Paris and blackboard chalk are made (mined in Montmartre) Click to show or hide the answer
Nephrite is one of two types (along with jadeite) of Click to show or hide the answer
Black semi–precious stone – a form of lignite (derived from wood, decayed under great pressure) – and therefore not strictly a mineral; mined at Whitby in Victorian times. (In the Southern Hemisphere it was commonly formed from the Araucariacea or monkey puzzle tree, which was common at the appropriate time) Click to show or hide the answer
Fine white clay, used in porcelain and in medicines – named after the mountain in China that it was once obtained from (a.k.a. china clay) Click to show or hide the answer
Building stone quarried from near Maidstone since Roman times Click to show or hide the answer
Refined petroleum product used as fuel for jet engines Click to show or hide the answer
Semi-precious stone, prized since antiquity for its intense blue colour – source of the pigment ultramarine Click to show or hide the answer
Brown, fibrous coal with a low carbon content – not fully transformed into coal – mainly used in power stations Click to show or hide the answer
Opaque, green-banded mineral: a hydroxide of copper carbonate; name derives from its resemblance to the leaves of the mallow plant Click to show or hide the answer
Formed by the metamorphosis of limestone Click to show or hide the answer
Hydrated magnesium silicate, used to make clay pipes Click to show or hide the answer
Glossy, flaky, silicate material commonly found in igneous and metamorphic rocks – "the black mineral in granite" Click to show or hide the answer
Whitish variety of feldspar, used in jewellery from Roman times; name is derived from its coloured sheen or 'twinkle', which can be blue, grey, pink or green Click to show or hide the answer
Naturally occurring volcanic glass, usually black or dark in colour; named after an ancient Roman explorer who was said by Pliny to have discovered it in Ethiopia (not a true mineral because, as a glass, it is not crystalline) Click to show or hide the answer
Coober Pedy (peedy), Australia, is famous for the mining of Click to show or hide the answer
Term used for a flawless diamond of 99 carats or more Click to show or hide the answer
Gem-quality olivine (a silicate of magnesium and iron) – found in varying shades of green, often mistaken for emerald Click to show or hide the answer
More common name for uraninite, the mineral in which Mme Curie discovered radium Click to show or hide the answer
Formed when volcanic lava cools; some samples float on water, at least until saturated Click for more information Click to show or hide the answer
The commonest rock–forming mineral, composed of silica Click to show or hide the answer
Common name for halite Click to show or hide the answer
The transparent red variety of corundum Click to show or hide the answer
Non–red corundum gemstones (typically blue) Click to show or hide the answer
Sandstone blocks found in quantity on Salisbury Plain, and elsewhere in that part of England – widely used by builders of Stonehenge, Avebury etc. Click to show or hide the answer
Europe's main source of sulphur since ancient times, and especially during the Industrial Revolution Click to show or hide the answer
The commonest mineral: a compound of the two most abundant elements in the earth's crust. Quartz, flint, jasper, opal, and chalcedony are all forms of Click to show or hide the answer
French chalk (tailor's chalk) is made from Click to show or hide the answer
Opaque, blue–green mineral: a hydrated phosphate of copper and aluminium Click to show or hide the answer
Sphalerite – known to (19th century) miners as black–jack – is the chief ore of Click to show or hide the answer

© Haydn Thompson 2017