Introduction
A mineral can be defined as a naturally occurring chemical compound or element formed as a result of an inorganic or geological process. A mineral is a homogenous compound that has a definite chemical composition which is generally not fixed. It is also characterized by an atomic arrangement that is always ordered (Nickel, 1995). According to Zussman (1992), minerals are differentiated from each other by their specific characteristics that are as a result of the types of atoms used to form them and the arrangements of these atoms inside the minerals. When a mineral is formed in open space, it assumes a natural shape referred to as a crystal form. This form reflects the arrangements of atoms inside the mineral and the chemical composition of the mineral (Busbey, Coenraads, Roots & Willis, 2007).
The most common minerals are Silicates and they make up over 90 percent of the Earth’s surface. This is because the constituent elements for the formation of silicates are Silicon and Oxygen and they make up around 75 percent of the Earth’s crust. This implies that the occurrence of various mineral species and their abundance is influenced by the chemicals present on Earth. Various geological changes like temperature, Earth’s pressure and the composition of a rock of Earth’s mass may bring about changes in the mineral composition of that rock of mass. However, it should be noted that the bulk composition of the rock of mass can be maintained but chemical composition will change if the conditions mentioned above change (Busbey, et al, 2007).
Geological environments of various minerals
Sedimentary minerals
These are minerals that are either found in wet and low temperature environments or in high temperature environments. These minerals are normally not affected by chemical weathering like other minerals. An example of a high temperature sedimentary mineral is quartz. These minerals contain a range of solubilities with some being highly soluble and other s being highly insoluble. Highly soluble sedimentary minerals include calcite and halite and they are mainly found in evaporate deposits. Highly insoluble sedimentary minerals include diamond, gold and quartz and these are found in detrial sedimentary rocks that are very coarse. Other less resistant minerals in this category include feldspars and are found in finer soils such as mudstones and siltstones. This therefore means that sedimentary minerals can be classified into two: Detrial sedimentary minerals and Evaporite sedimentary rocks (Busbey, et al, 2007).
Igneous Minerals
These are minerals that are found in igneous rocks. These minerals solidify at temperatures in excess of 800 º C and therefore have very high melting points. Igneous rocks are either basic or mafic igneous rocks or acidic or silicic igneous rocks. Acidic or silicic igneous rocks normally contain a lot of silica in their composition while basic or mafic igneous rocks contain relatively less silica. It should be noted that there is another category of igneous mineral environment which is referred to as pegmatite (PEG). These minerals are formed during the last stages of the formation of igneous minerals. These igneous rocks are very course grained and they are normally very similar to silicic igneous rocks in terms of chemical composition (Busbey, et al, 2007).
Hydrothermal minerals
When igneous rocks liquefy as a result of high temperatures, they form very hot solutions which are responsible for the formation of hydrothermal minerals. These rocks are mainly sub-classified into high temperature minerals, oxidized minerals and low temperature hydrothermal minerals. These are normally responsible for metals that occur in sulfide minerals and are generally referred to as chalcophile elements. Sulfide minerals are mainly found in hydrothermal rocks. However, there are cases where they have been found in metamorphic or igneous rocks. Oxidation causes sulfide minerals to weather. This is due to the fact that the presence of oxygen destabilizes them. Oxidation of sulfide minerals results in the formation of carbonates of the chalcophile metals, sulfates and oxides. Examples of low temperature hydrothermal minerals are gold and cassiterite while examples of high temperature hydrothermal minerals are silver and tungstate minerals (Busbey, et al, 2007).
Metamorphic minerals
These are minerals that crystallize from other minerals instead of through normal weathering and are characterized by instability in high temperatures. These are divided into high grade metamorphic minerals such as sillimanite and staurolite, and low grade metamorphic minerals such as zeolites and chlorites. The difference in the method of formation of these minerals is the main way of differentiating them from other minerals. It is therefore important to be keen on such differences when identifying and classifying these minerals (Busbey, et al, 2007).
Conclusion
Recently, there have been various advances in the fields of x-ray absorption spectroscopy and high resolution genetics which have led to the revelation that biological micro organisms are also may also be involved in the process of mineral formation. Various research studies have therefore been commissioned by scholars and biologists in order to be able to determine the validity of this revelation and the magnitude of their contribution to the formation of minerals. It has been discovered for a long time, bacteria are some of the influencing organisms of mineral formation. It is therefore important to understand how various minerals are formed in order to be able to use them in an environmentally friendly manner (Warren & Kauffman, 2003).
Technological advancements have made it easier for the identification of various minerals and biologists are therefore able to identify minor differences in the composition of minerals. This has led to the increase the number of different minerals that have been classified and accepted by various biological and scientific bodies all over the world. The discovery that living organisms are also responsible for mineral formation has given rise to a new area of research where researchers are now focusing on identifying the different micro organisms that have this ability. Focus is also on the identification of the various minerals that have been formed as a result of the actions of the micro organisms.
This however does not mean that there is less focus on the minerals that are formed through the normal process of chemical weathering (Warren & Kauffman, 2003). It is therefore suggested that scholars, researchers and scientists in general should ensure that all the factors that lead to the formation of minerals are identified and the resulting minerals are correctly classified in order to avoid cases of use of the wrong mineral. This will help in avoiding cases of accidents where the wrong minerals are used to manufacture a particular product and when the product used it causes negative effects to the users whether living or non living.
References
Busbey, A.B., Coenraads, R.E., Roots, D. & Willis, P. (2007). Rocks and Fossils. San Francisco: Fog City Press.
Nickel, E. H. (1995). The definition of a mineral. The Canadian Mineralogist, 33 (3): 689–690.
Warren, L. A. & Kauffman, M. E. (2003). Microbial Geo-engineers. Science, 299 (5609): 1027–1029.
Zussman, D.H (1992) An Introduction to the Rock Forming Minerals Second Edition, London: Longmans.