Principles of Metallurgy
"Metallurgy is the process of extraction of metals from their ores".
Human history in terms of materials had the Bronze Age and Iron Age pertaining to the metals they started to use the bronze and iron. Now we have more than 75% metals among the elements available.
Occurence of metals in nature
The earth crust is the major source of metals.Sea water also contains some soluble salts such as sodium chloride and megnesium chloride etc,.Some metals like gold(Au), silver(Ag), and copper(Cu) are avaible in nature in free state as they are least reactive.Other metals mostly found in nature in the combined form due to their more reactivity. The elements or compounds of the metals which occur in nature in earth crust are called Minerals. At some places, minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it.The minerals from which the metals are extracted from it. The minerals from which the metals are extracted without economical loss are called Ores.
Aluminium, for example, is the most common metal in Earth's crust, occuring in most of the minerals. However, it isn't economically feasible to extract it from most of these minerals. Instead the usual ore from which it is profitable to extract it is Bauxite--which contains from 50-70% of aluminium oxide.
* The ores of many metals are oxides and sulphides.
This is why oxygen-sulphur group is called chalcogen family.
The metals like K,Na,Ca,Mg, and Al are so reactive that they are never found in nature in free state.
The metals like Zn,Fe,Pb etc,. are moderately reactive. They are found in earth crust mainly as oxides,sulphides and carbonates.
Metals like Au,Ag are least reactive and they are found even in free state in nature.
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