Category: Geography Notes PPT

Understanding the stratigraphy meaning becomes quite simple when you get familiar with the stratigraphy principle of geology. Stratigraphy is a branch of geology that deals with the description of rock or interpretation of geologic time scale. It also renders insight into the geologic history of strata. As a geological discipline, stratigraphy takes into account the spatial location and temporal sequence of rock bodies. With the help of stratigraphy, bodies of rock are dated and interlinked with each other. Stratigraphic studies are mainly conducted to study sedimentary and volcanic layered rocks.

The Stratigraphic Principle

Stratigraphy organizes bodies of rock chronologically and spatially in accordance with their contained characteristics. It puts indirectly connected rock units together in a relationship. Stratigraphy is the substructure for remodelling the Earth’s history. It also plays a part in solving general geological questions.

The stratigraphic principle was initially introduced in 1669 by Nicolaus Steno in his documented work ‘Dissertations prodromus’. It has been founded and formulated on the foundation that, with a smooth sequence of sedimentary layers, the layer in the footwall (below) is older (matured) than the layer in the hanging wall (above).

Types of Stratigraphy

Following are the most important sub-disciplines in stratigraphy with their elements of study:

1. Lithostratigraphy (Lithostratigraphic unit)

2. Biostratigraphy (Zones)

3. Chronostratigraphy [(Chronostratigraphic units) {Age, Period, Epoch}]

4. Magnetostratigraphy (Reversals, chrons)

5. Sequence stratigraphy (Allostratigraphic units)

6. Pedostratigraphy – (Pedostratigraphic unit)

7. Geo Chronostratigraphy — (Geochronostratigraphic unit)

8. Chemostratigraphy (Isotope zones)

Stratigraphic Relationship

There are two types of contact in stratigraphy i.e.: conformable and unconformable.

1. Conformable: Non-fragmented accumulation, no breakages or hiatus (interruption or impairment in the continuity of the geological record). The resulting surface strata are known as conformity. Further, there are two forms of contact between conformable strata: abrupt contacts (directly isolated beds of distinctly distinguished lithology, minor depositional break, referred to diastems) and gradational contact (steady change in deposition, mixing zone).

2. Unconformable: Period of weathering/non-deposition. The surface stratum resulting is known as an unconformity. There are further

Four Kinds of Unconformity:

Angular Unconformity: younger sediment lies upon a weathered surface of folded or slanted older rocks. The older rock steeps at a different angle from the younger.

Disconformity: the contact between older and younger beds is noted by apparent, non-uniform weathering surfaces. Paleosol might form right above the disconformity surface due to the non-deposition setting.

Nonconformity: comparatively young sediments are accumulated right above older igneous or metamorphic rocks.

Paraconformity: the bedding planes below and above the unconformity run parallel to one another. A time gap exists, as depicted by a faunal break, but there is no weathering, just a period of non-accumulation.

Stratigraphic Subdivision

1. Concept of Zone

With respect to stratigraphic subdivision, there is the concept of stage. A stage is a crucial subdivision of strata, each minutely following each other while bearing a unique, distinctive assemblage of fossils. Thus, stages can be described as a group of strata consisting of the same major fossil assemblages. French palaeontology Alcide d’Orbigny is felicitated for the introduction and implementation of this concept. He named stages after geographic localities with specifically finer sections of rock strata that carry the characteristic fossils on which the stages are established.

2. Concept of Zone

The zone is an elementary biostratigraphic unit. The thickness of the unit ranges from a few to hundreds of metres, and its extent ranges from local to global. Biostratigraphic units are further classified into 6 principal kinds of biozones that are as below: 

1. Assemblage Biozones: These are strata that consist of a special correlation of three or more taxa.

2. Abundance Biozones: These are strata in which the abundance of a specific taxon or group of taxa is considerably higher than in the adjacent part of the section.

3. Concurrent Range Biozone: It includes the coincident, concurrent or overlapping part of the range of two particular taxa.

4. Interval Biozone: It includes the strata between two particular biostratigraphic surfaces. It can be established on either the highest or lowest occurrences.

5. Lineage Biozone: These are strata consisting of species demonstrating a particular segment of an evolutionary lineage.

6. Taxon Range Biozone: It depicts the known stratigraphic and geographic range of formation of a single taxon.

Sequence Stratigraphy

Sequence stratigraphy is an evaluation of sedimentary deposits in a time-stratigraphic aspect. It generally includes subdividing a sedimentary basin fill into individual sequences of accumulation (thus the name), which can then be associated with alterations in the two elementary parameters of sediment supply and shelter (the amount of space available for accumulation). A key purpose of this is to reconstruct how sediments filled a basin and thus, how the stratigraphy occurred through time and space. This can enable geologists and scientists to identify many significant aspects like finding out where fine and coarse-grained sediments are located and how sea level changed.

Uses of Sequence Stratigraphy

Over the years, sequence stratigraphy has transpired to be an extensively used, methodological framework that confines many contexts of sedimentology and stratigraphy and has different useful applications and anticipating capacities.

Tectosilicate, also known as framework silicate, is any element of a group of compounds having a structure that has silicate tetrahedrons(each of which includes central silicon atoms surrounded by four oxygen atoms at the corners of a tetrahedron). Each of the four oxygen atoms of a given tetrahedron is joined with another tetrahedron. Each tetrahedron is further connected to four others. Tectosilicate, along with the quartz and other silicate minerals having a chemical formula consisting of some multiples of SiO₂.

What is Tectosilicate?

Tectosilicate or Framework silicate is the substantial group of silicates consisting of approximately 75% of the earth’s crust. Framework silicates are identified by the three-dimensional structure of silica tetrahedra. Tectosilicate examples are the members of the quartz, feldspar, and zeolite group of minerals. Excluding the quartz group, they are considered as aluminosilicates with the general chemical formula AlXSiyO2(x + y))x-(1:2 ratio of Si to O atoms). 

The tectosilicate can include extra cations if some of the silicates are substituted by additional lower charge cations such as aluminum to give an overall negative charge. This replacement can also occur in other forms of silicates.

Some sparse minerals may consist of more than one type of anion coinciding in their crystal structure, or they may include complex anions that are halfway between the types written above.

Tectosilicate Definition

Tectosilicate is defined as the polymeric silicates in which silicon oxygen tetrahedral groups are correlated by splitting all their oxygen atoms with other groups so as to form three dimensional structure or network.

Tectosilicate  Fórmula

The general formula of three-dimensional or tectosilicate or framework silicate is (SiO₂)n. All the oxygen atoms of Si04 are united with other tetrahedra and hence forming the three dimensional network.

Eg SiO₂- quartz, tridymite, cristobalite- These oxide minerals are the crystallized form of silica. 

Three-dimensional  aluminosilicates are formed when Sio44- gets replaced with AlO45-.

Eg. Feldspar, zeolites  and Ult etc.

Tectosilicate Structure

Tectosilicate structure is made up of interconnected tetrahedra moving externally in all directions forming an intricate framework. All the oxygen is combined with other tetrahedra in the lower groups. In the nearly pure form of oxygen and silicon, the most predominant mineral found is quartz(SiO2). 

Aluminum can easily be substituted for the silicon ion in the tetrahedron. In other classes, this occurs to a certain degree but it is the biggest factor of the diversified structure. 

While tetrahedron is approximately the same as aluminum at its center, the charge is now a negative (-5) instead of a negative (-4). As the charge in a crystal must be balanced, additional cations are required in the tectosilicate structure and this is the basic reason for the maximum variations in the lower groups.

Tectosilicate Examples

The tectosilicate group includes the most abundant minerals composing the Earth crust. These includes

Quartz – 12%

Plagioclase Feldspar – 39%

Orthoclase Feldspar – 12%

Some Tectosilicate Examples Include: 

Orthoclase – KALSi₃O₈

Anorthite – CaAl₂Si₂O₈

Labradorite – (Ca, Na)(Al, Si)₄O₈

Albite – NaAlSi₃O₈

Quartz – SiO₂

Did You Know?

• Tectosilicate is a group of silicates that consists of all four oxygen atoms from each tetrahedron sharing themselves.

• The tectosilicates that contain Al are commonly known as plagioclase or feldspar.

• Feldspar is the name of the group of rocks forming tectosilicate minerals that comprise as much as 60% of the Earth’s crust.

• Tectosilicates represent almost 60% of the rock crust of the Earth. The Silicate group and feldspar group are the two most important groups.

Tors are typically the exposed rock mass of the jointed and broken blocks. These tors are known as either castle koppie or kopje by geomorphologists. Also, these tors large, free-standing outcrops of rocks that rise abruptly from the surrounding slopes that are smooth and gentle as they are a part of the rounded hill summit or the crest of a ridge. It is also a term that is commonly used in the southwest of England for hills especially the hills and the high points located in Dartmoor in Devon and Bodmin Moor of Cornwall. Tor meaning is from the English language which defines it as a bare mass of rock that is surmounted and surrounded by groups of blocks and boulders which is further derived from the old English word ‘torr’.

How Tors are Formed?

As per the Tor meaning, it is clear that they are exposed forms of rocks. Hence, it is clear that the rots are the landforms which are the landforms created due to the erosion and weathering of the rock that surrounds it. The surrounding rocks are mostly composed of granites but also contain shists, dolerites, dacites and ignimbrites and also coarse sandstones and others. The tor geography depicts its height as less than 5 meters. Many of the hypotheses that are laid down to understand how tors are formed have tried to propose and explain their origin but yet this topic remains a part of discussion amongst geologista, geomorphologists and physical geographers. An agreed-upon hypothesis states that the tor geography was formed by the geomorphic processes that differ widely in type and duration. These differences are said to be the attributes of the regional and local differences that occur in the climate and the different rock types. 

An example of tor geography explaining how tors are formed is the Dartmoor granite which was emplaced almost around approximately 300 million years ago. This happened along with the erosion of the cover rocks. Due to this erosion, the Dartmoor granite rock lay exposed to the chemical and physical weathering processes. Wherever the joints are found to be closely spaced, the large crystals present in the granite stone readily disintegrated which resulted in the formation of a sandy regolith which was locally known as growan. This is found to be readily stripped off by using the solifluction process or also by the surface wash when it was not protected by vegetation. This process significantly continued during the prolonged phases of cold climate during the Quaternary Ice ages which are known as periglaciation. 

Wherever the joints are found to be unusually widely spaced, the cores blocks are known to survive and escape the above-mentioned weathering processes. As a result, they formed the tors. These tors can be monolithic like the ones at Haytor and Blackingstone Rock or subdivided into stacks as more usually found and often arranged in the form of avenues. Each of the stacks is known to comprise several layers or tiers or pillows, which may have become separated. In this case, the rocking pillows are known as logan stones. Furthermore, these stacks are found to be vulnerable to frost action and are often collapsing which is understood from the trails of blocks present down the slopes known as clitter or clatter. Weathering also gives rise to the circular ‘rock basins’ formed by the accumulation of the water and the repeated freezing and thawing as found in the case of Kes Tor on Dartmoor. 

In the region of Dartmoor, when 28 tors were subjected to the process of dating, it showed that most of them are still young. This is determined as most of them are less than 1,00,000 years old and none of them is over 2,00,000 years old. They must have probably emerged at the start of the last major ice age – the Devensian. In contrast to this, the Scottish Cairngorms are other classic granite tor concentrations found in Britain with the oldest tors amongst them being between 200 and 6,75,000 years old and also the glacially modified regions having dates in-between 100 to 1,50,000 years. These tors reflect a more dry and more arctic climate. 

An image of the Tor is shown below: 

Before learning about the different types of minerals, we will first understand what are minerals. They are formed by geological processes and are usually found inorganic and solid in nature. There are also few organic materials, such as silver, gold, diamond etc they are found in the earth’s crust. Today, there are more than thousands of minerals recognized but only a few of them are common. A mineral is formed through natural processes and it possesses definite chemical composition. We can identify minerals by their characteristic of physical properties such as crystalline structure, hardness, streak, and cleavage. Different gemstones like diamonds, emeralds and sapphires that are produced in industries are identical. Hence they are called man made minerals.

In this article we will explain the classification of minerals, how are minerals classified and the importance of how we classify minerals.

How Many Types of Minerals?

Minerals are mostly classified based on their crystal form Classification of minerals is of two types namely metallic and non-metallic.

1. Metallic Minerals

Metallic minerals have lustre property in their appearance and they consist of metals in their chemical composition. These minerals serve as a potential source of metal and we can extract it through mining. Manganese, iron ore and bauxite are examples of metallic minerals. Metallic minerals can further be divided into two types : ferrous and non-ferrous metallic minerals.

Ferrous minerals mostly contain iron whereas non-ferrous minerals do not contain iron elements.

2. Non-metallic Minerals

Non-metallic minerals are minerals that either show a non-metallic lustre or shine in their appearance. The concentration of available metals is not present in their chemical composition. Limestone, gypsum, and mica are the most common examples of non-metallic minerals.

• Bauxite ore mostly exists in deeply weathered rocks. Volcanic rocks contain bauxite deposits in some regions.

• Iron metal extracted from iron ore. It never exists in the pure form we have to extract it from iron ore by eliminating the impurities.

• Gold is the oldest and most precious element that is known to us.

• Manganese ore is a silvery brittle or in the form of grey-white metallic ore that occurs in many forms and we can find it worldwide.

Chemical Composition of Minerals

Nearly about 98.5% of Earth’s crust is made up of only eight elements. These eight elements are oxygen, silicon, aluminium, iron, calcium, sodium, potassium, and magnesium. These are the elements that are made up of most minerals.

All minerals have a specific chemical composition. The silver mineral is made up of only silver atoms and diamond is made only made up of carbon atoms, but most minerals are made up of chemical compounds. Each mineral has its own chemical formula. Quartz is made of two oxygen atoms bonded to a silicon atom, and its formula is SiO₂. If a mineral contains any other elements in its crystal structure, then it is not quartz. A hard mineral that has covalently bonded carbon is known as diamond, but a softer mineral that also contains calcium and oxygen along with carbon is known as calcite.

The structure of calcite shows the relationship with calcium (Ca), carbon (C), and oxygen (O) minerals.

Some minerals have a range of chemical composition. Olivine is always made up of silicon and oxygen as well as iron or magnesium or it contains both.

Mineral Classes

Minerals are classified according to their chemical properties. Except for the native class element, the chemical basis for classifying minerals is the anion. It is the negatively charged ion that usually shows up charge at the end of the chemical formula of the mineral. For example, the sulfides are based on the sulfur ion, and it is represented as S^2-. Pyrite, for example,FeS₂ , is a sulfide mineral. In some cases, the anion is of a mineral class is in the form of polyatomic, such as (CO₃)^2-, it is the carbonate ion. The major classes of minerals are given below:

• silicates

• sulfides

• carbonates

• oxides

• halides

• sulfates

• phosphates

• native elements

Silicates

Silicate is a polyatomic anion, (SiO₄)^4-, which is the tetrahedral shape. Most minerals that are found in the earth’s crust are silicate minerals. All silicate minerals are built of silicon-oxygen tetrahedra (SiO₄)^4- in different bonding arrangements that form different crystal lattices. 

Sulfides

These are based on the sulfide ion, S^2-. Various examples include pyrite FeS₂, galena PbS, and sphalerite ZnS in its pure zinc form. Some sulfides are mined as sources of metals like zinc, lead, copper, and tin.

Carbonates

These are based on the carbonate ion, (CO₃)^2-. Calcite, CaCO₃, and dolomite are carbonate minerals. Carbonate minerals dissolve relatively easily in water, especially in acid water, and natural rainwater is slightly acid.

Oxides

These are based on the oxygen anion, O^2-. Different types of iron oxides include hematite Fe₂O₃ , magnetite Fe₃O₄, and pyrolusite MgO.

Halides

Halides have a halogen element present in the anion form, whether it be fluoride F^–, chloride Cl^–, bromide Br^–, iodide I^–, or astatide At^–. Halite, NaCl, is a halide mineral.

Sulfates

Sulfates have the polyatomic sulfate ion, (SO₄)^2-, present in the anion form. Anhydrite, CaSO₄, is a sulfate.

Phosphates

Phosphates have the polyatomic phosphate ion, (PO₄)^3-, as the anion. Fluorapatite,Ca₅(PO₄)₃F, which makes our teeth hard, is a phosphate mineral.

Native Elements

These elements are made of only a single element. Gold (Au), native copper (Cu), diamond and graphite are made of carbon, are they all are native element minerals. Therefore, the elements that are purified and crystallized in a laboratory do not qualify as minerals, until and unless they have also been found in nature.

Examples of Minerals

Minerals are solid substances found in nature. They are not alive. The atoms which made up a mineral are fitted together to form a crystal. The chemical composition of these kinds of atoms is in the form of crystals. It is the same for every crystal of that kind although impurities or matter that is not part of the crystal may be included. Gold, diamond, rock salt and graphite is used to make the “lead” of pencils.

A piece of green coloured plastic may look identical to the emerald structure. The Mols hardness test a streak test, colour, luster, cleavage and fracture are all ways of identifying minerals.

Uses of Minerals

Mineral like copper is used in electrical equipment as it is a good conductor of electricity. Clay is used to making cement etc which helps in constructing roads. Fibreglass cleaning agents are made of borax. Given below are the uses of minerals in our everyday life:

• Uses of minerals in the body

• Uses of metallic minerals

• Economic uses of minerals

Various other applications of minerals are used in constructing the building, developing weapons for defence, machinery, making of jewellery, synthesizing fertilizers etc.

Physical Properties of Minerals

Following are the physical properties of minerals:

• Colour: It refers to the colour of the mineral.

• Streak: It refers to the colour of the mineral’s powder.

• Luster: It refers to the way light reflects off the mineral’s surface.

• Specific Gravity: It refers to how heavy the mineral is relative to the same volume of water.

• Cleavage: It refers to the mineral’s tendency to break along flat surfaces.

• Fracture: It refers to the pattern in which a mineral breaks.

• Hardness: It refers to what minerals it can scratch and what minerals can scratch it.

Conclusion:

As we have discussed, a substance referred to as a mineral, which is a naturally occurring, inorganic, crystalline solid that has a characteristic chemical composition and crystal structure. The atoms in minerals are arranged in regular, repeating patterns that can be used to identify that particular mineral. It is classified on the basis of their chemical composition, and they are expressed in their physical properties. This module describes the classification of minerals the physical properties that are commonly used to identify minerals. They are colour, crystal form, hardness, density, luster, and cleavage. Also, we know how many types of minerals are there and their characteristics.

Resources are basically anything that is used to provide benefits to humans. The term ‘resources’ is usually used in the context of natural resources which are un-exhaustible and renewable. Mineral resources, as the name suggests, are resources that come from minerals. Energy resources, on the other hand, encompass all sources of energy, both renewable and non-renewable. 

So, what are minerals? Well, as per the Geologists, a homogeneous naturally occurring substance with a definable internal structure is called a mineral which is found in various forms in nature. The formation of the particular mineral depends upon the physical and chemical conditions of the material. 

Minerals are the greatest gift of nature, and these minerals help in the development of a country in all spheres. There are various types of minerals present in nature that are obtained from rocks or other sources. In this article, you will learn about minerals and resources, the main types of minerals, etc. It will help you to understand some of the very important concepts of Geography, which will help you in all the higher classes of Geography. 

This page classifies minerals and energy resources along with their types in detail.

Classification of Minerals

There are various types of minerals that are classified below. They can be divided into three categories.

Metallic Minerals

These are those minerals that contain iron or other metallic elements in their composition, which are generally found in igneous and metamorphic rocks. They can be formed in different products after melting. The different kinds of minerals are discussed here. 

1. Ferrous Minerals: These are those minerals that contain iron. For example, iron ore, manganese ore, nickel, and cobalt. These minerals provide the base for metallurgical Industries’ development.

2. Non-Ferrous Minerals: These are those minerals that don’t contain iron as their larger composition, for example, gold, silver, lead, bauxite, aluminium, nickel, tin, titanium, etc.

Non-Metallic Minerals

These are the minerals that are good for cement, glass, ceramics, and lime products Industries. These minerals are found in sedimentary rocks or young fold mountains and cannot be formed into other products after melting. For example, sand, clay, marble, limestone, etc.

Distribution of Different Types of Minerals in India

India is one of the richest countries in terms of mineral resources. The distribution of some minerals are mentioned below:

Iron Ore

India is rich with fine quality iron ore, which is the base and backbone of the industrial sector. There are various forms of iron ore as well, in which Magnetite has iron ore up to 70% and is the finest iron ore and Hematite is the most important in terms of quantity used and having 50-60% iron ore. The distribution of iron ore in India is represented in the following pie chart as per the 2016-17 data:

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Manganese

This mineral is mostly found in South or Central India which is used for the production of steel and ferroalloys, bleaching powder, insecticides, paints, etc. The distribution of manganese in India is represented in the following pie chart:

Copper

It is used in electrical cables, electronics, and chemical industries. India has a deficiency of this mineral. The distribution of copper in India is represented in the following map. 

Following are the major producer of copper:

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Bauxite

Clay-like substances such as alumina or aluminium are obtained from bauxite. This mineral is formed due to the decomposition of the wide variety of rocks having aluminium silicates. In India, this is found in the Amarkantak plateau, Maikal hills, and the Bilaspur-Katni region. The state of Andhra Pradesh is an important producer of this mineral. The distribution of this mineral in India is represented by the following chart:

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Limestone

It is found in rocks having the composition of calcium carbonate or calcium and magnesium carbonates. It is generally found in sedimentary rocks and works as a basic mineral for the cement industry. The distribution of this mineral is represented in the following chart:

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Types of Minerals 

Minerals can be broadly classified into two types on the basis of their occurrence: metallic and non-metallic. Metallic minerals are those that are found in the form of solid masses of metal, for example, gold, silver, copper, etc. Non-metallic minerals, on the other hand, are not found in the form of metals and include materials such as coal, limestone, etc. 

Minerals are found in nature in the form of rocks. The three main types of rocks are: igneous, sedimentary, and metamorphic. Igneous rocks are formed when molten rock (magma) solidifies. This can happen either on the earth’s surface (extrusive igneous rocks) or beneath the earth’s surface (intrusive igneous rocks). Sedimentary rocks are formed by the deposition of solid material from a liquid or gas. The most common type of sedimentary rock is limestone, which is made up of the shells of marine organisms. Metamorphic rocks are formed when one type of rock is changed into another through extreme heat or pressure. 

There are around 4000 known minerals, of which only about 20% are used commercially. Metallic minerals are generally more useful than non-metallic minerals. The main metallic minerals are gold, silver, copper, lead, zinc, etc. Non-metallic minerals can be further classified into two types: fuel minerals and industrial minerals. Fuel minerals are those that are used to produce energy, for example, coal and oil. Industrial minerals are those that are used in the manufacturing of various products. For example, limestone is used to make cement. 

Mode of Occurrence of Minerals

An “ore” means the accumulation of any mineral mixed with other elements where these minerals are found. There are the following forms in which they occur:

• They are found in the cracks, crevices, faults or joints, etc., in the Igneous and metamorphic rocks. Veins are called smaller occurrences, and loads are called larger occurrences. For example, tin, copper, zinc, and lead, etc.

• They are also found in the beds or layers of the sedimentary rocks, which have been formed because of accumulation, deposition, etc. For example, coal, gypsum, potash salt, etc.

• They are also found in the process of decomposition of surface rocks and leaving weathered & residual mass material, for example, bauxite etc.

• They are also found in alluvial deposits and ocean waters.

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Energy Resources and their Types

Minerals are also classified into energy resources. There are various sources of energy such as coal, petroleum, natural gas, etc., which are non-renewable resources, and other sources of energy are solar energy, wind energy, etc., which are non-renewable resources. 

They are of two types:

1. Conventional Sources of energy are those which are traditionally used, such as coal, petroleum, etc.

2. Non-Conventional Sources of energy are those which are not traditional but considered modern sources of energy such as solar energy, tidal energy, wind energy, etc.

Coal

Coal is one of the most important and most used sources of energy in India. It took millions of years to form this source of energy. 67% of India’s energy requirements depend on coal. Various types of coal are:

• Anthracite

• Bituminous

• Lignite

• Peat

The following map represents the coal distribution in India:

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Petroleum

It is the second most vital source of energy in India which acts as a raw material for a number of Industries in India. Mumbai High is the major producer in India. The distribution of oil refineries are represented in India are given below:

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Natural Gas

It is also a very important source of energy that acts as a raw material for various industries like petrochemical industries. It is a mixture of hydrocarbon gas, mainly methane but also includes other gases as well. It is an environmentally friendly source. The distribution of reserves of natural gas are represented in the following map:

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Solar Energy

It is a non-renewable source of energy that is directly obtained from the Sun and which will never be exhausted. It is an example of clean energy that reduces carbon footprints as well and helps in reducing electricity bills. India has great potential for this form of energy as it is a tropical country, and India is working on using its full potential. The following map shows the potential of India in terms of solar energy:

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Wind Energy

It is also a non-renewable energy source that is environmentally friendly and depends upon the location of usage. This is clean energy and has less operating cost as well. India has not used its full potential in this regard and is still working on it. The following map shows the wind power potential of India:

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Tidal Energy

Power is obtained by converting the energy of the tides into electricity and other power with the help of modern technology. The mechanical energy is converted into electrical energy through various methods using the tides. India has great potential for this form of energy as well because it is surrounded by three water bodies from three sides. The following map shows the potential of tidal energy in India:

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Here, we have covered the various important chapters of Geography, i.e. minerals and energy resources. These notes will help the students of Class 9 or higher classes to understand minerals and resources. After going through these notes, you will be able to answer the questions like explain minerals, how many types of minerals and resources are there etc. These notes will help the students to create a base of understanding regarding the minerals and resources.

From our context, we understand that  minerals are found from ore and they are classified into metallic, non-Metallic, and energy minerals. Chapter 5 – Minerals and Energy Resources has a great significance in Class 10 Geography exam. Students need to study all the topics related to minerals, their classification and types along with this, 

energy Resources, conventional Resources, non-Conventional Resources, Geothermal Energy, and conservation of energy resources. You may find the PDF from this page.

The stable type of calcium carbonate under high pressure is the aragonite, which is a widespread mineral. It can be characterised by its greater hardness and specific gravity from the more typical type of calcium carbonate calcite. Aragonite is often to be found in the oxidising zone of ore minerals, in serpentine and other rocks, in soil and in deposits of iron-ore, at low temperatures close to the surface of the Earth. The mineral Aragonite is usually found in pearls. It is polymorphous with calcite, vaterite and potentially reverses it to calcite in normal conditions over time (the same chemical formula but different crystal structures).

Aragonite is the important mineral in the shells of many marine invertebrates. These animals may secrete the mineral from water which would usually produce limestone; they do this using not entirely understandable physiological mechanisms.

Aragonite is a metamorphous carbonated gemstone found naturally in stalactites or in the hot springs. Due to its small, and branch-like crystal shapes, this type of aragonite is sometimes referred to as floss ferri. The mother-of-pearl lining of the mollusk shells contains a further cause of Aragonite. It is separated by the mantle of mollusks in pearl oysters, and builds the nacre layers which the oyster uses to produce the pearl itself. The several thin layers of aragonite add the perl-like lustre and elegance to the abalone shell.

Formation & Colors

Aragonite naturally forms the calcareous endoskeleton of warm and cold-water corals in almost all mollusk shells (Scleractinia). Aragonite tubes are present in some serpulids. Due to the close biological monitoring of mineral deposition in mollusk shells, certain shapes of crystal are different from those of inorganic aragonite. The whole shell of some mollusks is aragonite; in some aragonite forms only distinct sections of a bimineralic shell (aragonite plus calcite). An iridescent material, called ammolite, is made up of the nacreous layer of some extinct ammonite fossil shells.

Aragonite also occurs as inorganic precipitates in the oceans and in caves respectively such as marine cements and speleothems. Aragonite in serpentinites, where high Mg in pore solutions seem to inhibit calcite growth and favour aragonite precipitation, is not unusual.

Aragonite is metastable at the surface of the Earth at low pressures and thus usually substituted in fossils with calcite. Aragonite is largely unknown and older than Carboniferous. It can also be synthesised in water-ethanol mixtures at ambient temperatures by adding a solution of calcium chloride to the sodium carbonate solution at temperatures above 180 °C (140 °F).

The “sputnik” variety from Morocco is the most popular Aragonite on the market. They almost always have an amber hue, golden brown but can also look colourless. Other common color varieties of Aragonite include blue aragonite, pink aragonite, white aragonite, red aragonite, green aragonite, and orange aragonite.

Calcite Aragonite

The composition of calcium carbonate forms as Aragonite as well as Calcite, and the crystallisation of these two minerals only differs. In trigonal crystals, calcite, the more common mineral, forms while aragonite forms orthorhombic crystals. Aragonite and Calcite crystals are sometimes too small to be measured individually and these two minerals can only be distinguished by optical or x-ray tests. Without complex testing it may also be impossible to know the real identity of microcrystalline types of aragonite or calcite, which may also confuse these species.

The greatest Aragonite crystals are the twinned growth of the pseudohexagonal trilling three individual crystals. Even though the orthorhombic system crystallises Aragonite, most prismatic crystals are formed hexagonally due to twinning. Trillings can be distinguished from each individual member crystal through their multi-directional basal striations.

After aragonite, additional minerals may form pseudomorphs. Calcite after Aragonite, which is a pseudomorph after an established paramorph, is a particularity of the mineral universe. Some available aragonite crystals are in fact calcite after aragonite. Copper after Aragonite is an uncommon but common pseudomorph. Sand inclusions which give a sample the brown colour, may also contain aragonite.

As a deposition product from hot mineral-rich springs, an especially interesting type of Aragonite is present. When the water comes out of spring, calcium is released, and mounds and thick crusts are formed around sources. They could be sculpted and called “Onyx Marble” and “California Onyx,” if these are banded.

Most organic substances such as pearls and corals are made up primarily of aragonite. Pearl and mother-of-pearl have an iridescent surface that is essentially the layer of aragonite that has mollusks and associated invertebrates. Some types of aragonite, especially Flos Ferri, are fragile and fragile and can break easily when touched. Such samples must be very careful.

Aragonite and calcite, due to the nano and microstructural structures of the general architecture, are the two calcium carbonate polymorphs that give the shell of molluscan bivalves their strength and elasticity. Nacre, or pearl’s mother, is not yet classified as osteoinductive. It consists of Aragonite and produces the vertebrate bone.

Physical Properties of Aragonite Crystals

Aragonite’s crystal structure behaves like a prism, since it has three triangular sides, or orthorhombic structure. This quality prism, usually called “orient” in pearls, brings light through a diffracted range of gleaming colour. The most notable “orient” of Tahitian pearls is the thousands of aragonite layers that are used to cover the pearl seed. Let’s examine all the following properties:

• Chemical Formula: CaCO3

• Composition: Calcium carbonate, sometimes with some strontium, lead, and zinc.

• Variable Formula: (Ca,Sr,Pb,Zn)CO3

• Color: Colorless, white, brown, gray, yellow, red, pink, purple, orange, blue, green

• Hardness: 3.5 – 4

• Crystal System: Orthorhombic

• Crystal Forms and Aggregates: Pseudohexagonal trillings, in the form of elongated prismatic crystals or short tabular ones, are the most common crystallised habit. Unusually in individual crystals, untwinned. There are several aggregate types of pseudo hexagonal crystals including acicular, radiating, fibrous, stalactitic, botryoidal, oolitic, tuberose, granular, embedded and ball-like protrusions.

• Transparency: Transparent to opaque

• Specific Gravity: 2.9 – 3.0

• Luster: Vitreous, dull

• Cleavage: 3,1 – prismatic ; indiscernible,2

• Fracture: Subconchoidal

• Tenacity: Brittle

• Other ID Marks: 

1) May fluoresce blue, pink, yellow, or cream.

2) Clear specimens display a visible double refraction.

• Complex Tests: Effervesces in acids, even if cold and diluted.

• In Group: Carbonates; Aragonite group

• Striking Features: Poor cleavage, twinning habits, strong effervescence, and low hardness

• Environment: Sedimentary and evaporite deposits, deposits of hot spring, hydrothermal ore, igneous traprock and metamorphic schist habitats.

• Rock Type: Igneous, Sedimentary, Metamorphic

Characteristics of the Mineral

Aragonite is a calcite that can be found mostly in sedimentary rock. Calcite becomes limestone. Aragonite has a similar calcite chemistry, but its composition, symmetry, and various crystal shapes are different. Blue, brown, black, gold, green, grey and white is available in aragonite colour. It is primarily mined in Spain, Bolivia, Mexico, Morocco, Namibia, UK and the USA. Some shapes are very delicate. When struck, Aragonite quickly splits. The mineral also has sand, and some of the minerals are brown.

Aragonite Gemstone

Perls are also regarded as gemstones, but they are not. They are rocks, partially from aragonite. Aragonite is the key ingredient of pearls and coral in particular. The colour of the stones stems from the process that starts in oysters. Perles are made of aragonite on their surface. We have already discussed that argonite forms in different colours such as blue aragonite, pink aragonite, white aragonite, red aragonite, green aragonite, and orange aragonite.

Aragonite Uses

• In aquaria, the replication of the reef conditions, aragonite is considered important.  Aragonite supplies the essential materials for the long life of the sea and also retains the pH of the water close to its natural level to avoid biogenic calcium carbonate dissolution.

• Aragonite has been tested successfully for removal from polluted wastewater pollutants such as zinc, cobalt and lead.

• Some water conditioning companies say that their technology transforms calcite to aragonite for limescale reduction.

Conclusion

The stable type of calcium carbonate under high pressure is the aragonite, which is a widespread mineral. Aragonite is often to be found in the oxidising zone of ore minerals, in serpentine and other rocks, in soil and in deposits of iron-ore. It is metastable at the surface of the Earth at low pressures and thus usually substituted in fossils with calcite. The mineral is also found as a metamorphous carbonated gemstone found naturally in stalactites or in the hot springs. It can also be synthesised in water-ethanol mixtures at ambient temperatures.