Introduction to Ore-Forming Processes. Laurence Robb

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– (Cu,Ag)12As4S13

      3 Enargite – Cu3AsS4

      Oxides and Hydroxides

      This group of minerals is variable in its properties but is characterized by one or more metals in combination with oxygen or a hydroxyl group. The oxides and hydroxides typically exhibit ionic bonding. The oxide minerals can be hard, dense, and refractory in nature (magnetite, cassiterite) but can also be softer and less dense, forming as products of hydrothermal alteration and weathering (hematite, anatase, pyrolusite). Hydroxides, such as goethite and gibbsite, are typically the products of extreme weathering and alteration.

      Oxides

      1 Cuprite – Cu2O

      2 Hematite – Fe2O3

      3 Ilmenite – FeTiO3

      4 Hercynite – FeAl2O4

      5 Gahnite – ZnAl2O4

      6 Magnetite – Fe3O4

      7 Chromite – FeCr2O4

      8 Rutile – TiO2

      9 Anatase – TiO2

      10 Pyrolusite – MnO2

      11 Cassiterite – SnO2

      12 Uraninite – UO2

      13 Thorianite – ThO2

      14 Columbite‐tantalite – (Fe,Mn)(Nb,Ta)2O6

      Hydroxides (or Oxyhydroxides)

      1 Goethite – FeO(OH)

      2 Gibbsite – Al(OH)3

      3 Boehmite – AlO(OH)

      4 Manganite – MnO(OH)

      Oxysalts

      The carbonate group of minerals form when anionic carbonate groups are linked by intermediate cations such as Ca, Mg, and Fe. Hydroxyl bearing and hydrated carbonates can also form, usually as a result of weathering and alteration. The other oxysalts, such as the tungstates, sulfates, phosphates, and vanadates, are analogous to the carbonates, but are built around an anionic group in the form .

      Carbonates

      1 Calcite – CaCO3

      2 Dolomite – CaMg(CO3)2

      3 Ankerite – CaFe(CO3)2

      4 Siderite – FeCO3

      5 Rhodochrosite – MnCO3

      6 Smithsonite – ZnCO3

      7 Cerussite – PbCO3

      8 Azurite – Cu3(OH)2(CO3)2

      9 Malachite – Cu2(OH)2CO3

      Tungstates

      1 Scheelite – CaWO4

      2 Wolframite – (Fe,Mn)WO4

      Sulfates

      1 Baryte(s) – BaSO4

      2 Anhydrite – CaSO4

      3 Alunite – KAl3(OH)6(SO4)2

      4 Gypsum – CaSO4·2H2O

      5 Epsomite – MgSO4·7H2O

      Phosphates

      1 Xenotime – YPO4

      2 Monazite – (Ce,La,Th)PO4

      3 Apatite – Ca5(PO4)3(F,Cl,OH)

      Vanadates

      1 Carnotite – K2(UO2)(VO4)2·3H2O

      Silicates

The bulk of the Earth's crust and mantle is made up of silicate minerals that can be subdivided into several mineral series based on the structure and coordination of the tetrahedral anionic group. Silicate minerals are generally hard, refractory, and translucent. Most of them cannot be regarded as ore minerals in that they do not represent the extractable part of an ore body, and the list provided below shows only some of the silicates more commonly associated with mineral occurrences as gangue or alteration products. Some silicate minerals, such as zircon and spodumene, are ore minerals and represent important sources of metals such as zirconium and lithium, respectively. Others, such as kaolinite, are mined for their intrinsic properties (i.e. as a clay for the ceramics industry).

      Tekto (framework)

      1 Quartz – SiO2

      2 Orthoclase – (K,Na)AlSi3O8

      3 Albite – (Na,Ca)AlSi3O8

      4 Scapolite – (Na,Ca)4(Al,Si)4O8)3 (Cl, CO3)

      5 Zeolite (analcime) – NaAlSi2O6·H2O

      Neso (ortho)

      1 Zircon – Zr(SiO4)

      2 Garnet (almandine) – Fe3Al2(SiO4)3

      3 Garnet (grossular) – Ca3Al2(SiO4)3

      4 Sillimanite – Al2SiO5

      5 Topaz – Al2SiO4(F,OH)2

      6 Chloritoid – (Fe,Mg,Mn)2(Al,Fe)Al3O2(SiO4)2(OH)4

      Cyclo (ring)

      1 Beryl – Be3Al2Si6O18

      2 Tourmaline – (Na,Ca)(Mg,Fe,Mn,Al)3(Al,Mg,Fe)6Si6O18(BO3)3(OH,F)4

      Soro (di)

      1 Lawsonite – CaAl2Si2O7(OH)2·H2O

      2 Epidote – Ca2(Al,Fe)3Si3O12(OH)

      Phyllo (sheet)

      1 Kaolinite

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