Minerals

Naturally occurring crystalline substances with defined compositions — mineral species in the strict sense, not varieties or trade names.

• Acanthite

  Ag2S

  Silver sulfide — the principal silver ore, and the mineral behind the silver rushes that built cities.

• Albite

  NaAlSi3O8

  The sodium end of the plagioclase series, and the most common feldspar in evolved granites.

• Anorthite

  CaAl2Si2O8

  The calcium end of the plagioclase series — the first feldspar to crystallise from a cooling basalt, and a major constituent of the lunar highlands.

• Apatite

  Ca5(PO4)3(F,Cl,OH)

  Mohs 5, the mineral phosphate rock is made of, and the mineral bones and teeth are made of — the same compound doing both jobs.

• Aragonite

  CaCO3

  The other calcium carbonate — same composition as calcite, different structure, and the form most shells are built from.

• Arsenopyrite

  FeAsS

  Iron arsenic sulfide — the commonest arsenic mineral, and the one that makes gold ore refractory and gold mining an arsenic problem.

• Azurite

  Cu3(CO3)2(OH)2

  The blue copper carbonate that slowly becomes the green one — which is why so many old skies have turned to foliage.

• Baryte

  BaSO4

  Barium sulfate — astonishingly heavy for a pale, non-metallic mineral, and the weight in the drilling mud of every oil well.

• Bastnäsite

  (Ce,La)CO3F

  A rare earth fluorocarbonate — the principal ore of the light rare earths, and the mineral behind most magnets in the world.

• Beryl

  Be3Al2Si6O18

  A beryllium aluminium silicate — the only ore of beryllium, and, coloured by traces of other elements, both emerald and aquamarine.

• Beta quartz

  SiO2

  The high-temperature form of quartz — hexagonal rather than trigonal above 573 °C, and the reason a fired ceramic body can crack on cooling.

• Bismuthinite

  Bi2S3

  Bismuth sulfide — the ore of the heaviest element that is, for practical purposes, not poisonous.

• Borax

  Na2B4O5(OH)4·8H2O

  A hydrated sodium borate from dried desert lakes — the source of boron, and the flux that made soldering and brazing possible.

• Calcite

  CaCO3

  Calcium carbonate — the mineral of limestone, marble, chalk and most shells, and the reference point for hardness 3.

• Cassiterite

  SnO2

  Tin dioxide, and effectively the only tin ore of economic importance.

• Chalcopyrite

  CuFeS2

  A brassy copper-iron sulfide, and the principal ore of copper.

• Chromite

  FeCr2O4

  Iron chromium oxide — the only ore of chromium there is, and therefore the mineral every stainless steel depends on.

• Cinnabar

  HgS

  Mercury sulfide — the only ore of mercury worth mining, and the source of vermilion, the most brilliant red available to painters for two thousand years.

• Cobaltite

  CoAsS

  A cobalt arsenic sulfide — the mineral that gave cobalt its name, from the goblin miners blamed for the poison it gave off.

• Columbite

  (Fe,Mn)(Nb,Ta)2O6

  An iron manganese niobate — half of coltan, the source of the tantalum in every phone capacitor, and one of the clearest cases of a mineral becoming a conflict.

• Corundum

  Al2O3

  Aluminium oxide — hardness 9, the mineral of ruby and sapphire, and a major industrial abrasive.

• Diamond

  C

  Carbon in a cubic lattice — the hardest naturally occurring substance, and one of the best thermal conductors known.

• Fayalite

  Fe2SiO4

  The iron end of the olivine series — dark, dense, low-melting, and a common product of iron smelting slag.

• Feldspar

  The most abundant mineral group in the Earth's crust — about six parts in ten of it, and the parent of most clay.

• Fluorite

  CaF2

  The mineral that gave fluorescence its name and fluorine its existence — Mohs 4, and the source of nearly every fluorine compound made.

• Forsterite

  Mg2SiO4

  The magnesium end of the olivine series — a refractory mineral that makes furnace linings and, in gem quality, peridot.

• Galena

  PbS

  Lead sulfide — heavy, metallic, splitting into perfect cubes, and the ore that has supplied nearly all the world's lead since antiquity.

• Graphite

  C

  Carbon in stacked sheets — soft, slippery, electrically conductive, and chemically identical to diamond.

• Gypsum

  CaSO4·2H2O

  A soft sulfate mineral that gives up its water when gently heated and takes it back on mixing — the basis of plaster.

• Halite

  NaCl

  Rock salt — the only mineral people eat, and for much of history a commodity worth fighting over.

• Hematite

  Fe2O3

  Iron oxide — the most important ore of iron, and the red pigment used since the Palaeolithic.

• Ilmenite

  FeTiO3

  Iron titanium oxide — the abundant titanium ore, lower grade than rutile and the source of most titanium actually produced.

• Lepidolite

  K(Li,Al)3(Si,Al)4O10(F,OH)2

  A lilac lithium mica — the second lithium ore, and the main mineral source of rubidium and caesium alongside it.

• Magnetite

  Fe3O4

  The most magnetic naturally occurring mineral, a major iron ore, and the reason the compass exists.

• Malachite

  Cu2(CO3)(OH)2

  A green copper carbonate — an ore, the oldest green pigment, and a banded ornamental stone, all from the same weathered copper deposit.

• Microcline

  KAlSi3O8

  Potassium feldspar's low-temperature form — chemically identical to orthoclase, structurally ordered, and the source of the green gemstone amazonite.

• Molybdenite

  MoS2

  Molybdenum disulfide — the ore of molybdenum, a dry lubricant that works where oil burns, and so soft it marks paper like graphite.

• Monazite

  (Ce,La,Nd,Th)PO4

  A rare earth phosphate that carries thorium with it — the other major rare earth ore, and the reason their processing leaves radioactive residues.

• Muscovite

  KAl2(AlSi3O10)(OH)2

  The common pale mica — a mineral that splits into transparent sheets, and was window glass before window glass.

• Olivine

  (Mg,Fe)2SiO4

  The green magnesium-iron silicate that makes up most of the upper mantle — the most abundant mineral inside the Earth.

• Orthoclase

  KAlSi3O8

  The potassium feldspar of granite — the most abundant mineral group in the Earth's crust, and the raw material of porcelain.

• Pentlandite

  (Ni,Fe)9S8

  An iron nickel sulfide — the world's principal nickel ore, and the mineral behind most stainless steel and most battery nickel.

• Plagioclase

  (Na,Ca)Al(Si,Al)Si2O8

  A continuous solid solution from sodium to calcium feldspar — the commonest mineral series in the crust, and a thermometer for the magma that grew it.

• Pollucite

  (Cs,Na)2Al2Si4O12·2H2O

  A caesium aluminosilicate — essentially the only ore of caesium, and therefore of the atom that defines the second.

• Pyrite

  FeS2

  Iron sulfide — fool's gold — a mineral more valuable for the sulfur it yields and the acid it produces than for the iron in it.

• Pyrolusite

  MnO2

  Manganese dioxide — the main manganese ore, the black of cave painting, and the oxidiser inside a dry cell battery.

• Quartz

  SiO2

  The second most abundant mineral in the Earth's continental crust, and the reference point for hardness 7 on the Mohs scale.

• Rutile

  TiO2

  The richest natural form of titanium dioxide — the preferred feed for titanium metal and white pigment, and scarce enough that most producers use ilmenite instead.

• Scheelite

  CaWO4

  Calcium tungstate — a tungsten ore that fluoresces a startling blue-white, which is how it was prospected before instruments.

• Sperrylite

  PtAs2

  Platinum arsenide — the most important platinum mineral, and one of very few in which a platinum-group metal forms a mineral of its own.

• Sphalerite

  ZnS

  Zinc sulfide, the ore of nearly all zinc — and named for how thoroughly it deceives anyone trying to identify it.

• Spodumene

  LiAlSi2O6

  A lithium aluminium silicate from granite pegmatites — the hard-rock source of lithium, and the one that does not depend on a salt flat.

• Stibnite

  Sb2S3

  Antimony sulfide, in soft steel-grey blades — the ore of antimony, and the kohl of the ancient world.

• Strontianite

  SrCO3

  Strontium carbonate, named after the Scottish village it was found in — and the reason a firework burns red.

• Sylvite

  KCl

  Potassium chloride, laid down where ancient seas dried out — the mineral that is potash, and the potassium in fertiliser.

• Talc

  Mg3Si4O10(OH)2

  The softest mineral there is, and the one that defines the bottom of the hardness scale — soft enough to leave a mark on paper with a fingernail's pressure.

• Topaz

  Al2SiO4(F,OH)2

  Mohs 8, and the reason there is a step between quartz and corundum — a hard silicate whose main significance is as a reference point and a gemstone.

• Uraninite

  UO2

  Uranium dioxide — the principal uranium ore, the mineral the Curies worked, and the rock in which radium and polonium were found.

• Vanadinite

  Pb5(VO4)3Cl

  A lead vanadate that forms brilliant red hexagonal crystals in weathered lead deposits — and one of the few minerals vanadium concentrates in.

• Wulfenite

  PbMoO4

  Lead molybdate, in thin orange tablets — a minor ore of molybdenum and a mineral collected almost entirely for how it looks.

• Xenotime

  YPO4

  Yttrium phosphate — the ore of yttrium and, unlike monazite, the mineral that concentrates the heavy rare earths.

• Zircon

  ZrSiO4

  A tough silicate that traps uranium and refuses lead — which is how the age of the Earth is known, and the only real source of zirconium.