Occurrence of Metals
Metals are generally shiny and malleable in their pure form, but they are rarely found in this state in nature. Most metals occur as compounds, and their extraction requires specific processes.
Native Elements
Metals with low chemical reactivity, such as copper, silver, gold, and platinum, often occur in nature as native elements, meaning they are found in their pure form.
Combined State
More reactive metals, like the alkali metals (e.g., sodium, potassium), do not occur freely in nature due to their high reactivity. Instead, they are found in a combined state, typically as compounds, and must be extracted through metallurgical processes.
Minerals and Ores
Mineral
A mineral is a naturally occurring substance obtained through mining, containing metals either in their free state or as compounds such as oxides, sulphides, etc. While metals are present in small amounts in most minerals, only some contain a sufficient concentration to be economically viable for metal extraction.
Ore
An ore is a type of mineral that contains a high percentage of a metal, making it feasible to extract the metal profitably. For example, iron is found in around 800 minerals, but only those like hematite and magnetite, which have a high iron content, are considered ores of iron.
Example:
- Bauxite is an ore of aluminium because it contains a high percentage of aluminium, making its extraction economical.
- China clay (Al₂O₃·SiO₂·2H₂O) is also a mineral of aluminium, but the extraction of aluminium from china clay is not profitable, so it is not considered an ore.
Metallurgical Processes
The extraction of metals from their ores involves three main stages:
- Concentration of the Ore: The process of removing impurities (gangue) from the ore to increase the concentration of the metal of interest.
- Extraction of Crude Metal: The concentrated ore is then subjected to various metallurgical processes to extract the metal in its crude form.
- Refining of Crude Metal: The crude metal is purified to obtain the final, usable product.
|
Metal |
Occurrence |
Common Ore/Mineral |
|
Aluminium (Al) |
Combined State |
Bauxite (Al₂O₃·2H₂O) |
|
Iron (Fe) |
Combined State |
Hematite (Fe₂O₃), Magnetite (Fe₃O₄) |
|
Copper (Cu) |
Native State / Combined State |
Chalcopyrite (CuFeS₂), Malachite (Cu₂CO₃(OH)₂) |
|
Gold (Au) |
Native State |
Found as nuggets in riverbeds and rocks |
|
Silver (Ag) |
Native State / Combined State |
Argentite (Ag₂S), Native silver (Ag) |
|
Zinc (Zn) |
Combined State |
Sphalerite (ZnS), Zincite (ZnO) |
|
Lead (Pb) |
Combined State |
Galena (PbS) |
|
Platinum (Pt) |
Native State |
Found in native form, often alloyed with other metals |
|
Sodium (Na) |
Combined State |
Halite (NaCl) |
|
Magnesium (Mg) |
Combined State |
Magnesite (MgCO₃), Dolomite (CaMg(CO₃)₂) |
|
Tin (Sn) |
Combined State |
Cassiterite (SnO₂) |
|
Nickel (Ni) |
Combined State |
Pentlandite ((Fe,Ni)₉S₈) |
|
Titanium (Ti) |
Combined State |
Rutile (TiO₂) |
|
Chromium (Cr) |
Combined State |
Chromite (FeCr₂O₄) |
|
Cobalt (Co) |
Combined State |
Cobaltite (CoAsS), Erythrite (Co₃(AsO₄)₂·8H₂O) |
|
Manganese (Mn) |
Combined State |
Pyrolusite (MnO₂), Rhodochrosite (MnCO₃) |
|
Mercury (Hg) |
Combined State |
Cinnabar (HgS) |
|
Barium (Ba) |
Combined State |
Barite (BaSO₄), Witherite (BaCO₃) |
|
Lithium (Li) |
Combined State |
Spodumene (LiAl(SiO₃)₂), Lepidolite |
|
Calcium (Ca) |
Combined State |
Limestone (CaCO₃), Gypsum (CaSO₄·2H₂O) |
|
Potassium (K) |
Combined State |
Sylvite (KCl), Carnallite (KMgCl₃·6H₂O) |
|
Vanadium (V) |
Combined State |
Vanadinite (Pb₅(VO₄)₃Cl), Carnotite (K₂(UO₂)₂(VO₄)₂·3H₂O) |
|
Molybdenum (Mo) |
Combined State |
Molybdenite (MoS₂), Wulfenite (PbMoO₄) |
|
Tungsten (W) |
Combined State |
Wolframite ((Fe,Mn)WO₄), Scheelite (CaWO₄) |
|
Antimony (Sb) |
Combined State |
Stibnite (Sb₂S₃) |
|
Bismuth (Bi) |
Combined State |
Bismuthinite (Bi₂S₃), Native bismuth (Bi) |
|
Uranium (U) |
Combined State |
Pitchblende (U₃O₈), Carnotite (K₂(UO₂)₂(VO₄)₂·3H₂O) |
|
Thorium (Th) |
Combined State |
Monazite ((Ce,La,Th)PO₄) |
|
Zirconium (Zr) |
Combined State |
Zircon (ZrSiO₄) |
|
Cadmium (Cd) |
Combined State |
Greenockite (CdS) |
|
Palladium (Pd) |
Native State / Combined State |
Found with platinum, nickel ores |