Classification of Rocks on Different Basis

A naturally occurring and coherent aggregate of one or more minerals is called a rock in geology. These aggregates are the fundamental building blocks of the solid Earth, and they often take the shape of recognised and mappable volumes. Metallic nanocrystals and their granitic types cycle through many forms in the geologic cycle. Heat, stress, time, and severity of extreme weather events in the Earth’s crust and surface all play a role in the process. Weathering and transit to a deposition site are both examples of erosion. Diagenesis is the process of producing sedimentary rock through grain compaction and natural cementation, crystallisation from water or solutions, or recrystallisation, as previously mentioned. Lithification is the process of turning salt into rock.

Geological Classification of Rocks:

Sedimentary Rocks

• Sedimentary rocks originate on or around the surface of the Earth. 
• Precipitation, weathering, lithification, erosion and dissolution are the major geological processes that lead to the formation of sedimentary rocks. 
• Sedimentary rocks are classified into two groups. 
• The first is detrital rock, formed by the erosion and buildup of rock fragments, sediment, and other components collectively referred to as detritus or trash. 
• On the other hand, chemical rock is formed by the dissolving and precipitation of minerals.

Igneous Rocks:

• Igneous rocks are formed when magma cools and crystallises after eruptions on the earth’s surface or when the molten rock is inside the crust.
• All lava originates in the lower crust or part of the mantle because of the enormous heat beneath. Based on the lava solidification, igneous rocks can have a broad range of attributes.
• They can also take on varied appearances depending on time they take to cool. For example, depending on whether the magma cools rapidly or slowly, different rocks from the same magma can become rhyolite or granite. 
• Extrusive and intrusive igneous rocks are the two main types. Extrusive rocks are generated on the Earth’s surface from lava, which is magma that has risen from beneath the surface. 
• Intrusive rocks form as magma freezes within the planet’s crust.

Metamorphic Rocks:

• Metamorphic rocks are rocks that transform to generate a new rock. Metamorphic rocks are formed under highly particular conditions. 
• The existing rock must be treated with high temperature, air intensity, or hot, mineral-rich fluid. In most cases, all three of these requirements are met.
• These circumstances are most prevalent beneath the Earth’s crust or along plate boundaries where tectonic plates interact.
• To build metamorphic rock, it is vital that the present rock holds steady and does not melt.

Physical Classification of Rocks:

Stratified Rock:

• The deposition of things such as sand and silt near river beds causes stratified rocks to form. Later, these are stacked on top of one another to form layers. 
• As a result, they are referred to as stratified rocks. These rocks include sandstone, siltstone, and shale, to name a few. 
• Bedding is a prominent feature of sedimentary rocks, which are ‘piles’ of layers of sediments deposited one on top of another. 
• When studying rock strata involved in orogens, these principles come in handy. Sedimentary rocks are the only ones that have stratification. 
• Stratification is the process of stacking layers, one on top of the other, that differ in material, colour, texture, thickness, or all of these. 
• Stratification in sedimentary rocks can be favourable or bad.

Unstratified Rocks:

• Unstratified rocks have a crystalline or dense granular texture. 
• Throughout their entire body, they have a similar structure. The majority of igneous and sedimentary rocks are found beneath unstratified rocks.
•  Examples of the list of types of rocks include granite, marble, and traps.

Foliated Rocks:

• Foliated rocks have a layered or banded structure that results from pressure and heat exposure. 
• Metamorphism produces the majority of metamorphic rocks, which are classified as foliated rocks.
• Examples of the list of types of rocks include Gneiss, schist, slate, and other rocks are examples.

Chemical Classification of Rocks:

Argillaceous Rocks:

• Argil is a Greek word that means “clay.” As a result, argillaceous rocks have a high clay content. 
• These rocks are soft by nature and can easily disintegrate in the presence of water. Because of their brittleness, these rocks can easily be crushed in a dry state. 
• Argillaceous rocks include shale, slate, laterite, and others.

Calcareous Rocks:

• Calcareous rocks are those that contain a significant amount of calcium carbonate. 
• These are normally hard, but their durability is influenced by the surrounding constituents, which can react with calcium and reduce rock durability. 
• Calcium-rich rocks include marble, limestone, and dolomite, among others.

Siliceous Rocks:

• Siliceous rocks are those that have a high percentage of silica in them. 
• They are tougher and more durable due to a considerable amount of free silica. It also has a high level of weather resistance. 
• Siliceous rocks include granite, chert, quartzite, and others.

Conclusion:

Texture and Composition are the two parameters used to classify rocks. The texture of a rock is determined by the sizes and shapes of mineral grains and other elements and how these sizes and shapes interact. The process that created the rock is in charge of such factors. Because igneous, sedimentary, and metamorphic processes are all different, the textures are also different. The types of minerals and their proportions, or Mineralogy, are accepted as the natural expression of composition for this exercise and standard classification.