Crystal size
The earth is basically made up of minerals which are derived through various natural processes. These processes are continually taking place in the crust. Minerals are described as solid, organic or inorganic substances that exist naturally and have a specific structure and chemical formula. It is evident from analytical studies that nearly all elements in the crust are composed of a minimum of one mineral. Minerals have different colors, density, hardness, crystal size, crystal form, location, availability, transparency and composition.
Some of the minerals in the crust exist freely or in uncombined state because of their unreactiveness and they include sulfur, bismuth, platinum, old, copper and silver. Some minerals are referred to as uranophane in that they are radioactive while others are referred to as magnetite since they tend to be magnetic. There are also those minerals that have ability to glow with aggressive luminescence when they are exposed to ultra violet light; an example of such minerals is fluorite (Gulluly, 2000, 23).
The mineral that is known to be the most abundant in the earth’s crust is quartz (silicon dioxide) and feldspar (a potassium aluminum silicate). Human beings have great liking of minerals simply because of their unique and wonderful features like attractive colors and beauty. For example, certain samples of gemstones have a progression of watermelon like green to pink color running from one side of a crystal to the other. Moreover, there are others with rainbow like colors.
Despite being very attractive and interesting some of the minerals are duping; some people who are not used to gold, which is the most precious of all mineral, have been deceived using other minerals that resemble pure gold like the pyrite (Fool’s Gold) and lost a lot of money in the process. Among all the known minerals, diamond has been known to be the most hardest. In addition, it has been prized for long as the most coveted mineral because of its stunning interaction with light.
Normally, most of the diamonds have many impurities and are not good for gemstones; alternatively they are used for industrial purposes or even they are modified to meet this demand. When minerals are processed and refined they are referred to as gems. The processing and refinery involves cutting and polishing of the minerals. Gems are famous world wide because of their high monetary value and they are used as jewelries and decorations. It is important to note that some of the gems are not derived from minerals.
An example for such gem is pearl which is gotten from an oyster. The gems that fetch the highest value world wide are minerals called precious stones and they include the sapphrires, rubies, diamonds and emeralds. The most popular gems globally are topaz, emerald, diamond, sapphire, opal, Amethyst, ruby and aquamarine (Adams, 2003, 86). When different minerals combine they form rocks. It is therefore true that we can say minerals are mined from rocks. For instance, quartz is a mineral that is derived from granite.
When granite is mined, it is usually a composed of various minerals where quartz is one of them. To obtain quartz from this composition, granite (the rock) is crushed processed and refined. Fundamentally, there are three main types of rocks that are known by the geoscientists. They are: the sedimentary rocks, metamorphic rocks, and the igneous rocks. Igneous rocks are usually solid crystals which are formed directly from cooling magma. Magma refers to the molten or liquefied solid materials found in the earth’s interior.
The process of formation of this type of rocks is purely exothermic, meaning heat is involved in the process. The formation of these rocks entails transformation of the molten material which is in liquid phase, to solid phase (state). The earth is generally made up of igneous rocks especially where they are exposed to cold weather or space which results to the process of cooling the hot magma from the planet’s interior. Magma is normally contained in the earths interior in what is referred to as magma chambers .
These chambers are characterized by very high temperatures and low pressure which allow the heated materials to expand and exist in liquid form. As the magma swells, it finds areas of weakness in the crust where it penetrates through to find its way either to the surface or somewhere near the surface. Due to this, various types of igneous rocks are produced. The basic types are: the intrusive igneous rocks and the extrusive igneous rocks. The extrusive igneous rocks refers to the rocks that are formed when the molten material from the underneath reaches the surface and cools down.
On the other hand, the intrusive igneous rocks are formed when the molten materials unsuccessfully penetrates the earths crust and cools down under the surface to form a solid rock (Anderson, 2000, 67). There are two prime features that can also be used to classify the igneous rocks; that is, texture and composition. Texture is attributed to the size of the mineral grains in the final rock. The size and texture of the grain is partly determined by the speed of cooling of the magma.
In this point of view, gradual cooling process results to formation of big grains while rapid cooling result to formation of small grains. In this regard, since the cooling process on the surface is very quick, the igneous rocks with small grains are categorized under the extrusive rocks whereas the ones with large grains are categorized as intrusive because the cooling process is slow under the surface. Intrusive rocks are usually fine in texture while the extrusive rocks are usually coarse in texture depending on the rate of cooling down as explained above.
When it comes to the aspect composition, it is assumed that intrusive igneous rocks consists of many minerals while the extrusive rocks are composed of few minerals. This is because the gradual cooling process under the surface provides time for accumulation of many minerals unlike the rapid cooling on the earth’s surface that does not permit collection of materials (Gulluly, 1998, 27). The sedimentary rocks are formed from slow deposition of materials on surface or under water to form a layer of a thin veneer of deposits. This type of rocks is also called the basement rock.
The materials pile over a period of time to form a layer of consolidated materials which finally form a layer of rock. The materials that are deposited may be organic or inorganic. The organic materials are derived from parts of living organisms like animals skeleton or plant remains while the inorganic materials are gotten from the existing rocks or dissolved minerals in waters. The inorganic deposits are derived through physical processes of weathering, collision and erosion or through chemical processes like corrosion, dissolution and precipitation.
Classification of sedimentary rocks is based on three broad categories which are: clastic sedimentary rocks, chemical sedimentary rocks and organic sedimentary rocks. Sedimentary rocks are mainly identified by looking for stratifications in a sample of a rock. Examples of this type of rocks include calcite, silicates, ferrocite, turbidites and shale including many others (Earney, 1997, 102). The last type of rocks is the metamorphic rocks. This type of rocks is formed from the existing ones, that is, igneous and sedimentary rocks.
The rocks are subjected to transformation, while in their physical state which does not change their mineral composition through adding or loss but in some cases fluids like water are lost. This change is as result of high temperatures and high pressure underneath. The factors that are involved in the metamorphic processes are: chemical composition, fluid components, temperature levels, pressures and time. Rock metamorphism can be categorized in two broad categories which are the regional metamorphism that is associated with continental mountain building processes and terrains metamorphism.
The terrain metamorphism is further categorized into contact metamorphism, catalistic metamorphism and hydrothermal metamorphism (Anderson, 2000, 75). In conclusion, it is evident that rocks are formed from a cyclic process that takes place in the physical, biological, chemical components of the environment. Minerals are of great importance to both plants and animals for their survival. In addition, they are of great economic value to man.
The vital role played by minerals, gems and rocks cannot be downplayed since the most wealthy people and their countries have their economic power anchored on mining. Work cited Adams Frank. The Birth and Development of Geological Sciences. Routledge, London, 2003, pp. 86 Anderson Ewan. Structure and Dynamic of US Government Policymaking: The Case of Strategic Minerals. Praeger Publishers, Westport CT, 2000, pp. 67, 75 Earney Fillmore. An Introduction to the Science of Geology. Macmillan Publishers, London, 1997, pp. 102 Gulluly James. The Principles of Geology. W. H Fremmil, 1998, pp. 23, 27
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