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		Talc
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		Gypsum
3	The most stable polymorph of calcium carbonate		Calcite
4	The colourful mineral form of calcium fluoride		Fluorite
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		Apatite
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		Orthoclase feldspar
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		Quartz
8	A silicate mineral of aluminium and fluorine: colourless in its pure form, but usually tinted by impurities; traditionally the birthstone for November		Topaz
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		Corundum
10	The hardest known natural material (mineral or other): an allotrope of carbon, highly valued as a precious gemstone		Diamond

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)		Alexander Pushkin
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		Amarillo Starlight
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		Argyle Pink Jubilee
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		Black Prince's Ruby
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)		Black Star of Queensland
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		The Centenary
Largest diamond ever found (South Africa, 1905) – cut into pieces, including the Great Star of Africa and the Second Star of Africa		The Cullinan
Largest diamond ever found, prior to the Cullinan (S. Africa, 1893)		The Excelsior
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		Graff Pink
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		Golden Jubilee Diamond
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		Heart of Eternity
Presented to Louis XIV by Jean Baptiste Tavernier and to Marie Antoinette by Louis XVI		The Hope
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		The Jonker
Once the largest known diamond – originated in India, became part of the British crown jewels 1877. Name means "mountain of light"		Koh–i–noor
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		Millennium Star
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)		Moussaieff Red
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		Pink Star
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		(Great) Star of Africa
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		Star of India
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)		Uncle Sam

Places

Armalcolite, tranquillityite and pyroxferroite are three minerals that were first found		On the Moon
Europe's main source of sulphur since ancient times, and especially during the Industrial Revolution		Sicily

Other

Four types of gemstone that aren't minerals (not an exhaustive list):

Fossilised resin from coniferous trees		Amber
Red or pink, made from the skeleton of a type of marine animal		Coral
Black, derived from wood that has changed under extreme pressure – a type of lignite		Jet
Produced in the soft tissue of a living shelled mollusc		Pearl

The four Cs that determine the value of a diamond:

Cut

Colour

Clarity

Carat (weight)

Snow–white variety of gypsum (calcium sulphate) – extracted in the English midlands since at least the 15th century		Alabaster
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		Amethyst
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		Anthracite
Semi–precious gemstone – a variety of beryl, pale blue or light green in colour: name is derived from the Latin meaning 'water of the sea'		Aquamarine
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		Asbestos
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)		Basalt
First discovered at Les Baux in southern France		Bauxite
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		Bentonite
Aquamarine, emerald, morganite and heliodor are coloured varieties of (colourless when pure)		Beryl
Medium–grade coal, about 60–80% carbon, named after the tar–like substance that it contains		Bituminous coal
Form of fluorspar (fluorite) found in the south Pennines – particularly in a famous cave near Castleton, Derbyshire; named for its blue and yellow staining		Blue John
Form of dolerite found in the Preseli hills of Pembrokeshire, extensively used in Stonehenge – named after the distinctive colour it appears when wet		Bluestone
Coal low in spores and algae, with no visible structure		Cannel coal
Agate, Onyx, Sardonyx, and carnelian are all forms of		Chalcedony
Sedimentary rock of which flint is a variety		Chert
Rocks that are rich in the clay mineral kaolinite are known as kaolin, or		China clay
Ore of mercury, used as the source of the brilliant red (scarlet) pigment known as vermilion, and associated red mercury pigments		Cinnabar
Variety of quartz – rare in nature, but produced artificially by heating amethyst or other quartzes: name is from the Latin for 'yellow'		Citrine
Saccharine is made from		Coal (tar)
Crystalline form of aluminium oxide, of which ruby and sapphire are forms		Corundum
Precious stone that is a green variety of beryl		Emerald
Mineral calcium fluoride; colourless when pure, otherwise violet, blue, yellow, brown, or green		Fluorite or fluorspar
Alternative name for iron pyrites or pyrite (mineral iron disulphide, FeS2)		Fool's gold
Coarse–grained igneous crystalline rock: typically composed of quartz, feldspar and mica		Granite
Crystalline form of carbon, sometimes known as plumbago or black lead, from which pencil leads are made		Graphite
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		Gritstone
Mineral calcium sulphate from which plaster of Paris and blackboard chalk are made (mined in Montmartre)		Gypsum
Nephrite is one of two types (along with jadeite) of		Jade
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)		Jet
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)		Kaolin
Building stone quarried from near Maidstone since Roman times		Kentish Rag
Refined petroleum product used as fuel for jet engines		Kerosene
Semi–precious stone, prized since antiquity for its intense blue colour – source of the pigment ultramarine		Lapis lazuli
Brown, fibrous coal with a low carbon content – not fully transformed into coal; often referred to as "brown coal"; mainly used in power stations		Lignite
Opaque, green–banded mineral: a hydroxide of copper carbonate; name derives from its resemblance to the leaves of the mallow plant		Malachite
Formed by the metamorphosis of limestone		Marble
Hydrated magnesium silicate, used to make clay pipes		Meerschaum
Glossy, flaky, silicate material commonly found in igneous and metamorphic rocks – "the black mineral in granite"		Mica
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		Moonstone
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)		Obsidian
Coober Pedy (peedy), Australia, is famous for the mining of		Opal
Term used for a flawless diamond of 99 carats or more		Paragon
Gem–quality olivine (a silicate of magnesium and iron) – found in varying shades of green, often mistaken for emerald		Peridot
More common name for uraninite, the mineral in which Mme Curie discovered radium		Pitchblende
Formed when volcanic lava cools; some samples float on water, at least until saturated		Pumice
The commonest rock–forming mineral, composed of silica		Quartz
Common name for halite		Rock salt
The transparent red variety of corundum		Ruby
Non–red corundum gemstones (typically blue)		Sapphires
Sandstone blocks found in quantity on Salisbury Plain, and elsewhere in that part of England – widely used by builders of Stonehenge, Avebury etc.		Sarsens
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		Silica (SiO2)
French chalk (tailor's chalk) is made from		Talc
Opaque, blue–green mineral: a hydrated phosphate of copper and aluminium		Turquoise
Sphalerite – known to (19th century) miners as black–jack – is the chief ore of		Zinc

© Haydn Thompson 2017–23