Types of Minerals

What is a mineral? To qualify for being called a mineral, a substance has to be in a solid state of matter and also have a crystalline atomic or molecular structure. It should also be a homogeneous, naturally occurring substance with a clearly defined chemical composition. In 1965, the International Mineralogical Association adopted a standard definition for minerals as 'an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes'. Many minerals are used for extracting useful metals from them, and hence, the study of different types becomes utterly important.

There are an overwhelming number of known minerals. Currently, the International Mineralogical Association lists more than 4,000 minerals, with new minerals still being discovered. Only 100 of these are commonly found, about 50 are found occasionally, while rest of these are very rarely encountered. To ease up the study of types of minerals and their uses, there are two broad categories in which they are divided into. Let us take a good look at this classification.

Silicate Minerals
The most commonly found group of mineral in the Earth's crust is the silicate group. Almost all silicate minerals have silicon and oxygen as their primary components. Most silicate minerals are formed by the cooling of molten rocks. As the molten rocks come closer to the surface inside the Earth's crust, they start cooling very fast and combine with the most abundant element in the Earth's crust, silicon. Silicate minerals constitute approximately 90% of the Earth's crust. Fayalite (Fe₂SiO₄)Zircon (ZrSiO₄), Enstatite (MgSiO₃), Ferrosilite (FeSiO₃) are some examples of sulfate minerals.

Non-silicate Minerals
There is a complete range of non-silicate minerals. Some of these are formed when there is cooling of magma, while some others are formed when water in them evaporates, or due to minerals decomposition. The non-silicates can be further classified in to different groups which are: elements, oxides, carbonates, sulfates, and many more which are not commonly found naturally. Most of these groups have their own sub-categories. But, let us discuss these groups first:

• Elements: Many pure elements are found in the form of minerals in ores or mines. For example, uncombined carbon is often found in its pure state in the form of graphite or more rarely as diamond. Gold, silver and sulfur are other elements which are also found in its pure state. Even though these are pure elements they qualify to be known as minerals, but no chemical process is required on them further.
• Oxides: When an ore is found in which one or more elements are combined with oxygen, it is an oxide mineral. These may have chemical formulas of type XO (MgO, ZnO, CuO, etc.), X₂O (Cu₂O), X₂O₃ (Al₂O₃, Fe₂O₃), XO₂ (MnO₂, SnO₂) and XY₂O₄ (MgAl₂O₄, FeCr₂O₄). The oxide minerals, are mostly of metallic elements. Example: hematite, magnetite, cuprite. Silicates and oxides are the most common types of minerals in volcanoes, especially after an eruption.
• Carbonates: The carbonate type of minerals are formed when a single carbonate ion (CO₃^2-) reacts with a metal ion of complementing polarity. Example: siderite (FeCO₃), smithsonite (ZnCO₃), calcite (CaCO₃). Carbonate minerals are used in making cement and other bonding material.
• Sulfate: The mineral class which includes the sulfate ion (SO₄^2-) within its molecular structure, is categorized as sulfate mineral. Minerals like Gypsum (CaSO₄·2H₂O) and Barite (BaSO₄) are examples of sulfate minerals.
• Organic Minerals: This class of minerals include biogenic substances, genesis or origin of which can be attributed to a geological processes. Organic minerals include all types of oxalates, mellitates, citrates, cyanates, acetates, formates, hydrocarbons, etc. Example of organic mineral includes whewellite, moolooite, mellite, fichtelite, carpathite, evenkite and abelsonite.

Apart from there are many more non-silicate minerals like nitrates, sulfides, halides, phosphates, etc. but most of the 4,000 odd listed minerals are grouped in the above categories. Make sure you do not confuse between minerals and rocks. A rock is a combination of a number of minerals which may also include organic remains and mineraloids i.e. non-crystalline minerals.

That concludes an overview of the various mineral types found on this planet. Hope, this write-up has succeeded in reiterating how important minerals and their type are for the sustenance of human kind on this planet.