UNIT-II MINERALOGY

MINERALOGY A mineral is naturally occurring homogeneous inorganic substance having distinctive physical properties and a more or less definite chemical composition. Minerals are to a large extent the units which make up the rocks of the earths crust or the outer shell.

MODE OF FORMATION OF MINERALS Three kinds of formation of minerals in nature Formed from magma Secondary process Metamorphism Directly formed from deposition of molten magma - feldspar, quartz, pyroxenes, amphiboles, micas Due to weathering, precipitation, deposition (secondary process) – calcite, dolomite, bauxite, coal, petroleum Formed under the influence of high temperatures and pressures with and without the active involvement of chemically active solution (metamorphism)- Garnets, chlorite, graphite

CRYSTALLOGRAPHY Great majority of minerals when the conditions of formations are favorable, occur in definite and characteristic geometric forms known as crystals. Crystal-Greek word “Krystallos” meaning clear ice. The study of crystals is called as crystallography.. “Crystals are bodies bounded by surfaces usually flat, arranged on a definite plan which is an expression of an orderly internal arrangement of the atoms”.

CRYSTALLOGRAPHIC ARRANGEMENT

SYMMETRY All crystals show by the arrangement of their faces a definite symmetry which enables one to group them into different classes Types of symmetry Plane of symmetry Axis of symmetry Centre of symmetry

SYMMETRY 1.PLANE OF SYMMETRY A plane of symmetry divides a crystal into two similar and similarly placed halves 2.Axis of symmetry If a crystal on being rotated comes to occupy the same position in space more than once in a complete turn the axis about which the rotation has taken Is called as axis of symmetry 3.Centre of symmetry A crystal is said to have centre of symmetry if an imaginary line can be passed from any point on its surface through its centre and a similar point can be found on the line at an equal distance beyond the centre

PHYSICAL PROPERTIES Colour Lustre Structure Hardness Cleavage Fracture Specific gravity Tenacity Odour and taste

Colour very useful in identifying mineral in spite of the fact that colour is constant in most of the minerals and commonly colour is due to stain or impurities in the minerals. Lustre Appearance of a fresh surface of a mineral in a ordinary reflected light Metallic- galena Glassy-vitreous Pearly-talc Structure Term used to denote the shape and form of minerals. Columnar Bladed Fibrous Radiated Lamellar granular

Hardness Resistance a mineral offers to abrasion or scratching and is measure relative to a standard scale of ten minerals known as Moh’s scale of hardness Cleavage Tendency of many crystallized minerals to break or split in certain parallel directions yielding more or less smooth surfaces known as cleavage planes. May be perfect and imperfect Fracture Appearance of the broken surface of the mineral. Specific gravity Specific gravity of a mineral is the ratio of its weight to the weight of an equal volume of water.

Tenacity The resistance which the mineral offers to breaking, crushing, bending or tearing-in short its cohesiveness is known as tenacity Ex Brittle, sec tile, malleable, flexible and ductile Taste A few minerals which are soluble in water have more or less characteristic tastes Acid, alkaline, astringent, bitter, cooling, pungent, saline

ISOMORPHISM Peculiar natural phenomenon Minerals appear to be mixtures of two different minerals from chemical composition. This type of formation is called as isomorphism Examples: Feldspar, pyroxene, amphiboles and garnets

ROCK FORMING MINERALS Silicate ranks first in the earths crust for rock forming minerals. SiO4 tetrahedron ins the fundamental unit of all silicate minerals. STRUCTURE OF SILICATES: Nesosilicates - SiO4 occurs as Independent unit E.g. garnet. Sorosilicate - SiO4 occurs as pairs unit E.g. garnet. Inosilicate - SiO4 occurs as chains along one direction or single chain silicates e.g. pyroxenes Cyclosilicates - SiO4 occurs as ring form as 3 or 4 units called as ring silicates e.g beryl Phyllosilicates - SiO4 occurs as sheets; called as sheet silicates. E.g mica, chlorite Tectosilicates - SiO4 occurs as three dimensional frame work e.g quartz, feldspar

MINERAL GROUP OR FAMILIES Some silicate minerals have similar atomic structure and chemical composition. Such set of minerals are called as groups or families. Examples of some important groups of silicate minerals Feldspar group Pyroxene group Amphibole group Garnet group

IMPORTANT DETAILS OF ROCK FORMING MINERAL I. FELDSPARS Most abundant of all the silicate minerals. The name refers to a group and not a single mineral Make up about half the rocks of earths crust Form monoclinic and triclinic crystals and are aluminous silicates of K, Na or Ca. Three common molecules Orthoclase - KAlSi3O3 Albite - NaAlSi308 Anorthite - CaAlSi3O8

CRYSTAL SYSTEM : MONOCLINIC Any mineral that falls under the following specifications belongs to the monoclinic crystal system. Three axes, all of them are unequal in length. Two of them are at right angles to each other, while the third is lies at an angle other than 90°.

CHEMICAL COMPOSITION-FELDSPAR In chemical constitution, felspars are chiefly Alumino-silicates of sodium, potassium and calcium with the following general formula : WZ4 O8 where W=Na ,K, Ca and Ba and Z= Si and Al . The Si : Al shows a variation of 3:1 to 1:1 . Some examples of chemical composition of felspar minerals are : KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8 Occurs in isomorphous series

ATOMIC STRUCTURE-FELDSPAR At atomic level ,the felspars shows a continuous three-dimensional network type of structure in which SiO4 tetrahedra are linked at all the corners, each oxygen ion being shared by two adjacent tetrahedral. The SiO4 tetrahedra is accompanied by AlO4 tetrahedra so that the feldspar are complex three dimensional framework of the above two types of tetrahedra. The resulting network is negatively charged and these negative charges are satisfied by the presence of positively charged K, Na, Ca and Ba. The felspar group of minerals crystallize only in two crystallographic systems Monoclinic and Triclinic.

CRYSTALLIZATION The feldsdpar group of minerals crystallize only in two crystallographic systems Monoclinic and Triclinic. CLASSIFICATION Chemically felspar fall into two main groups: The potash felspar The soda lime felspar . Common members of the two groups are - Potash felspar : Orthoclase (KAlSi3O8), Sanidine(KAlSi3O8) and Microline (KAlSi3O8). Soda – lime feldspar : These are also called the plagioclase feldspars and consists of an isomorphous series of six felspar with two components: NAlSi3O8 and Ca Al2 Si2O8 as the end members. 1. Albite 4. Labradorite 2. Oligoclase 5. Bytwonite 3. Andesine 6. Anorthite The above series is also known as Albite-Anorthite series.

Crystallographically ,felspar fall in two crystal systems . Monoclinic Feldspars 1. Orthoclase (KAlSi3O8 ) 2. Sanidine (KAlSi3O8 ) Triclinic Feldspars 1. Microcline (KAlSi3O8 ) 2. Albite – Anorthite series (six minerals)-(six minerals) PHYSICAL PROPERTIES In addition to their close relationship in chemical composition ,crystallography and atomic constitution ,felspar group of minerals exhibit a broad similarity and closeness in their physical characters as well so that differentiation of one variety from other requires very thorough, sometimes microscopic examination. Light in colour, lower specific gravity , have a double cleavage and a hardness varying between 6-6.5. COMMON TYPE OF MINERALS Orthoclase 2. Microcline 3. Albite 4. Anorthite

PHYSICAL PROPERTIES-FELDSPAR Form Tubular, mineral occurs as uniform thickness Colour Generally white, pale grey or pale red Streak White or pale body colour Lustre Vitreous Fracture Even to uneven Cleavage Two sets one set is better developed Hardness 6 Density Medium, 2.57 Occurrence weathering

Orthoclase Crystal system Monoclinic ; β=63•57•.Crystals commonly occur in prismatic shape. Cleavage Shows cleavage in 2 directions. The one parallel to basal pinacoid (001) is perfect. The cleavage angle is 90•. Colour Various shades of pink and red, such as flesh red, reddish white, light pink . The transparent variety is called the Adularia . Luster Vitreous to semiviterous. Hardness and specific gravity 6-6.5 ; 2.56 to 2.58 Composition KAlSi3O8 Optical Optically negative (-) Occurrence A most common and essential constituent of many igneous rocks ,especially granites . Economic use As a ceramic material. Varieties Adularia-a transparent orthoclase. Sanidinc-a high temperature variety stable above 900•C

microcline Crystal system Triclinic, resembles closely with orthoclase in crystal habits. Cleavage In two directions, the one parallel to basal pinacoid(001) is perfect. Colour Similar to orthoclase. In addition , may occur as a greenish felspar,when it is called amazonite. Streak ,hardness and specific gravity colorless, 6-6.5,2.54 to 2.57 Composition KAlSi3O8 Optical Optically negative (-). Occurrence It occurs along with the orthoclase in granites and other igneous rocks. Economic use As a ceramic material and semi-precious stone (amazonite). Varieties Anorthoclase (meaning-not orthoclase).It is a triclinic felspar containing sodium aluminum silicate.

albite Crystal system Triclinic ,it is the first member of the isomorphous plagioclase series . Cleavage Present in 2 directions. the one parallel to basal pinacoid (001)is perfect. Colour Commonly whitish or pinkish white but shows shades of grey,green and blue. Streak Colourless Luster Vitreous to pearly. Hardness and specific gravity 6-6.5 , 2.60-2.62 Composition Sodium aluminum silicate with NaAlSi3O8 - 100-90 % and CaAl2Si2O8 -0-10%. Optical Optically positive(+). Occurrence It is an essential constituent of many igneous rocks such as granite,syenites,rhyolites and dacites. Economic use As a ceramic material. As an ornamental stone in polished form.

anorthite Crystal system Triclinic, it is the last member of the isomorphous plagioclase series. Cleavage Present in two directions, the one parallel to basal pinacoid (001)if perfect . Colour Generally white, may also occur in reddish and light grey shades. Streak Colourless Luster Semi-vitreous. Composition CaAl2Si2O8 -100-90% Optical Optically positive (+) Occurrence An important constituent of many basic types of igneous rocks. Varieties Composition of other members of plagioclase felspars has mentioned above . These maybe broadly considered the varieties of plagioclase felspars.

II. QUARTZ Composition of SiO2 Most abundant material next to felspar Colourless or white Many coloured varieties are mainly due to impurities. Three main varieties Crystalline -Rock crystal, amethyst, rose quartz, milky quartz Crypto-crystalline -Chalcedony, carnclian Amorphous-opal Mostly used for jewellery and ornamental purposes

QUARTZ Crystal system Hexagonal, (rhombohedral). Crystals common ; some crystals weighing many tones have been reported. Twinned ,right-handed and left-handed crystals are common. Cleavage Generally absent Fracture Conchoidal Colour Colourless when pure, quartz also occur in coloured varieties :red, green , blue and mixture. Hardness 7 Sp. Gravity 2.65-2.66 Streak White in coloured varieties Varieties It is a very common rock forming mineral and occurs in numerous varieties . A few common varieties are mentioned below.

Polymorphous transformation Quartz, when heated , transforms into high temperature modifications as follows: (870•C) (1470•C) (1713•C) Quartz ↔ Tridymite ↔ Cristobalite ↔ melt The variety named as QUARTZ itself has two polymorphs : 1. Α quartz, 2. β quartz. Identification of the exact type of quartz (into Αand β) requires thoroug investigations of the mode of formation of mineral as observed by its place of occurrence and also type of symmetry. Right handed and left handed quartz : When occurring, quartz may be distinguished into right handed and left handed types. Carried out on the basis of recognition of some typical faces such as trigonal, trapezohedron and dipyramid. These two faces normally occur at the edges of the prism faces, one above the another. In the left handed quartz ,these faces are located on the left side of the upper edge of the prism, whereas in the right handed quartz, these occur on the right upper edge of the crystals. Such a location of these faces in manifestation of an internal atomic arrangement in the crystal.

COLOURED VARIETIES : Common pure quartz is a colourless transparent mineral. Presence of even a trace of an impurity may give it a characteristic colour and hence a variety . A few common types of quartz distinguished on their basis are : Amethyst – purple or violet Smoky- dark to light brown, even black Milky- pure white and opaque Rose red – colour is attributed to presence of titanium.

CRYPTOCRYSTALLINE TYPES : In many cases, crystalline of pure silica to quartz remains incomplete due to interruption in the process for one reason to another. Silica occurring in these cryptocrystalline varieties, although close in composition and physical properties to quartz is named differently. A few common varieties of cryptocrystalline silica are as follows : Chalcedony – luster ,waxy, commonly translucent, generally massive. Agate – often banded , opaque and massive. Onyx – a regularly banded agate having alternating and evenly paced layers of different colours. Flint – a dull opaque variety of chalcedony breaking with characteristic conchoidal fracture. Jasper- a dull red, yellow,almost amorphous variety of silica. OCCURRENCE Quartz and its varieties occur in all types of rocks ;igneous, sedimentary and metamorphic. In igneous rocks, quartz makes up bulk of acidic varieties. In sedimentary rocks quartz makes up sandstones and ortho quartzites. Loose sands consist mostly of quartz grains. The metamorphic rocks like gneisses contain good proportion of quartz in some cases. A metamorphic rock named as (Para) quartzite is entirely made up of quartz.

PIEZOELECTRICITY Quartz scepters Quartz crystals have piezoelectric properties; they develop an electric potential upon the application of mechanical stress. An early use of this property of quartz crystals was in phonograph pickups. One of the most common piezoelectric uses of quartz today is as a crystal oscillator. The quartz clock is a familiar device using the mineral. The resonant frequency of a quartz crystal oscillator is changed by mechanically loading it, and this principle is used for very accurate measurements of very small mass changes in the quartz crystal microbalance and in thin-film thickness monitors. Quartz scepters

PHYSICAL PROPERTIES-QUARTZ Form Granular or short prismatic Colour Black or dark greenish black; pale colour – magnesium rich pyroxene Streak White or pale body Lustre Vitreous Fracture Uneven Cleavage Two sets od prismatic cleavage 87° and 93° Hardness 5 to 6 Density Medium Specific gravity 3.2 to 3.5

III. PYROXENE Constitute important group of minerals that are generally recognized by their stout crystals and their two cleavages right angles to each other. Most pyroxenes are dark coloured Ca, Mg and Fe silicate composition Varieties Monoclinic pyroxene - Augite Orthorhombic pyroxene - Hypersthene

CHEMICAL COMPOSITION Composition mainly consists of silicates of calcium, magnesium and ferrous iron. At initial formation magnesium rich varieties At later stage iron rich formation General formula R2(AlSi)2 where R –divalent calcium, magnesium or ferrous iron ATOMIC STRUCTURE Single chain silicates Have 1:3 ratio of silicon and oxygen Mostly crystallize in the form of either orthorhombic or monoclinic system

Monoclinic pyroxene- AUGITE

AUGITE - description Chemical Formula: (Ca,Na)(Mg,Fe,Al)(Al,Si)2O6 Augite is an important rock-forming mineral, and large crystals are fairly common. It is the most widespread member of the pyroxene group, and it frequently alters to many other minerals, including Hornblende. Augite usually occurs in dull crystals that are ugly and uninteresting. The name Augite is derived from the Greek word augites, "brightness", in reference to the bright luster this mineral occasionally exhibits.

OCCURRENCE Major rock forming mineral in mafic igneous rocks, ultramafic rocks and some high grade metamorphic rocks.

Crystal System : Monoclinic Any mineral that falls under the following specifications belongs to the monoclinic crystal system: Three axes, all of them are unequal in length. Two of them are at right angles to each other, while the third is lies at an angle other than 90°.

AUGITE – PHYSICAL PROPERTIES Colour : dark green to black Streak : white to gray, augite can be slightly harder than a streak plate so brittle fragments rather than a powder will sometimes be produced. Lustre : vitreous Diaphaneity : translucent to opaque Cleavage : prismatic Hardness : 5.5 – 6 Specific Gravity : 3.2 - 3.6 Distinguishing Characteristics : Two cleavage directions almost at right angles, dark green to black colour Chemical Classification : silicate

USES OF AUGITE Augite is a dark green to black mineral that is used for ceramics. It contains large amounts of aluminum, iron, and magnesium and can be found in meteroic stones. ceramic glazing, manufacturing aluminum, purifying water.

IV.AMPHIBOLES Another type of mineral AMPHIBOLE MINERALS Important Crystallization ORTHORHOMBIC MONOCLINIC Crystals – long, slender, prismatic, sometimes fibrous Prism angle – 124’

Amphibole Group – Resemble – Pyroxene Group CHARACTERISTICS HARDNESS: 5 – 6 SPECIFIC GRAVITY: 3 – 3.5 Dark in Colour CHEMICAL COMPOSITION Amphibole minerals – Metal silicates – Si : O – 4 : 11 Ca, Mg, Fe, Mn, Na, K, H – metallic ions (OH) ions – F and Cl – Chemical Formula – [Si4 O11]2 [OH]2 Various ions – Al, Mg, Fe, Ca, Na, K, H, F – replaced – giving rise to a variety of Amphibole minerals ATOMIC STRUCTURE Difference – Amphiboles and Pyroxenes Amphiboles – SiO4 tetrahedra – double chains Reason – more complex than Pyroxenes – chemical composition

PHYSICAL PROPERTIES Orthorhombic Amphiboles Crystallise in only 2 crystal systems Dark in colour. Hardness – 5 to 6 Specific Gravity – 2.8 to 3.6 Elongated Slender Often fibrous in nature Orthorhombic Amphiboles ANTHOPHYLLITE (Mg, Fe)3 [Si4O11]2 [OH]2 CRYSTAL SYSTEM Orthorhombic – thin, slender fibres CLEAVAGE Perfect and Prismatic COLOR Grey, brownish or greenish HARDNESS 5.56 – 6 SP. GRAVITY 2.85 – 3.20 LUSTRE Vitreous OPTICAL Optically (+) OCCURRENCE Only in metamorphic rocks

VARIETIES OF AMPHIBOLES Hornblende Tremolite Actinolite Asbestos Hornblende is the most common variety

AMPHIBOLE - 1.Hornblende

Hornblende – Description Chemical formula : Ca2(Mg,Fe)4Al(Si7Al)O22(OH,F)2 Any of a subgroup of amphibole minerals that are calcium-iron-magnesium-rich and monoclinic in crystal structure. Hornblende, occurs widely in metamorphic and igneous rocks. Common hornblende is dark green to black in colour and usually found in middle-grade metamorphic rocks (formed under medium conditions of temperature and pressure). Such metamorphic rocks with abundant hornblende are called amphibolite's.

System : Monoclinic Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

OPTICAL PROPERTIES Colour : distinctly coloured, shades of green, yellow-green, blue- green and brown Composition : exhibits a wide range of compositions. Occurrence : common mineral found in a variety of geological environments, i.e. in igneous, metamorphic and sedimentary rocks Alteration : may be altered to biotite, chlorite or other Fe-Mg silicates Distinguishing Features : cleavage and grain shape, inclined extinction, pleochroism

PHYSICAL PROPERTIES Colour : dark green to black. Streak : gray to greenish gray Lustre : vitreous Diaphaneity : translucent to nearly opaque Cleavage : good Hardness : 5.0 - 6.0 Specific Gravity : 3.0 - 3.5

USES The hornblende mineral is used in a variety of common things that we use every day. These things include: steel, soap, oil, buildings, and statues.

Monoclinic Amphiboles – 2.Tremolite Ca2Mg5 [(Si4O11)]2 [OH]2 CRYSTAL SYSTEM Monoclinic –long, bladed CLEAVAGE Prismatic and Perfect COLOUR White to light grey HARDNESS 5.5 – 6.0 SP. GRAVITY 2.9 – 3.0 LUSTRE Vitreous OPTICAL Optically (-) OCCURRENCE Igneous and metamorphic rocks.. (mostly)

Monoclinic Amphiboles – 3. ACTINOLITE Ca2 (Mg, Fe)5 [(Si4O11)]2 [OH]2 CRYSTAL SYSTEM Monoclinic CLEAVAGE Perfect and Prismatic COLOUR Green due to ferrous ion HARDNESS 5.5 – 6.0 SP. GRAVITY 3.1 – 3.3 VARIETY Asbestos – fibrous form – long and flexible fibres

V. INTRODUCTION-MICA Mica is the name given to a group of silicate minerals that have silicon and oxygen as their two major components. The Mica family of minerals includes several variations based on chemical composition and characteristics.

Mica’s are besides feldspars, pyroxenes and amphiboles, very common rock forming minerals comprising approximately 4 percent of the Earth. They have great variation in their Chemical Composition. Despite this, mica minerals are easily grouped together because of their similar atomic structure. (Mica’s yield water when heated in a closed test tube.)

DIFFERENT TYPES

The 11 common variations are: Biotite Celadonite Fuchsite Glauconite Lepidolite Margarite Muscovite Phengite (or) Mariposite Phlogopite Sericite Stilpnomelane The many variations come from the diverse ways it formed. Mica formations are associated with volcanoes and hydrothermal vents.

GENERAL FORMULA X2Y4–6 Z8 O20(OH,F)4 Chemically, micas can be given the general formula X2Y4–6 Z8 O20(OH,F)4 in which, X is K, Na, or Ca or less commonly Ba, Rb, or Cs; Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.; Z is chiefly Si or Al, but also may include Fe3+ or Ti.

CHARACTERISTICS Mica has a brilliant shininess that glitters and sparkles. In fact the name mica is believed to have come from the Latin word ‘MICARE’ which means “to shine.” Mica is responsible for the flashes of light in composite rocks such as granite, gneiss, and slate. The crystal structure is monoclinic with a somewhat hexagonal crystal shape. These two characteristics are due to the structure of the atoms that make up the mica group.

PROPERTIES Name Content Color Streak Colorless Luster White, Yellowish, Green, Gray Streak Colorless Luster Vitreous to Pearly Transparency Transparent, Translucent and Opaque Crystal System Monoclinic Specific Gravity 2.8 Hardness(Mohs) 2.5-3 Cleavage Perfect

Fracture Uneven Uses Mainly as Insulators in Electronics Location Mica is found in many rocks around the world. Notable deposits are found in India, South Dakota, Russia and Brazil. Larger deposits are found in Colorado(USA), Evje(Norway) and Minas Gerais(Brazil).

BIOTITE

DESCRIPTION OF BIOTITE General Formula: K2(Mg,Fe)3 AlSi3O10(OH,O,F2)2 Biotite is a group of common rock-forming minerals forming a series between phlogopite and annite. The name is best used as a field name for dark micas for which the exact composition has not been determined.

DESCRIPTION OF BIOTITE – CONTD. Biotite survives a certain amount of weathering and is found in soils, sediments and sedimentary rocks. Weathered Biotite becomes relatively brassy of bronzy in colour and has been mistaken for gold. Its lower density, cleavage, and other properties are soon apparent to the careful observer. Finally Biotite can form as a result of hydrothermal processes, especially wall-rock alteration around ore veins.

OPTICAL PROPERTIES Colour: Typically brown, brownish green or reddish brown. Occurrence: Common in a wide range of igneous and metamorphic rocks and may be an important detrital mineral in sediments. Cleavage: Perfect cleavage on {001}. Twinning: Rarely visible. Optic Orientation: Extinction is parallel or nearly parallel, with a maximum extinction angle of a few degrees. Cleavage traces are length slow. Alteration: Alters to chlorite, clay minerals, and/or sericite, iron-titanium oxides, epidote, calcite, and sulphides Distinguishing Features : colour, "birds-eye" extinction, nearly parallel extinction

BIOTITE - PHYSICAL PROPERTIES Colour: black, dark green, dark brown Streak: white to gray. Lustre: vitreous. Diaphaneity: transparent to translucent. Cleavage: basal, perfect Hardness: 2.5 – 3 Specific Gravity: 2.7 - 3.3 Chemical Classification: silicate

BIOTITE - USES Biotite has very limited commercial use. Biotite particles are sometimes used as a surface treatment in decorative concrete, plaster and other construction materials. It is also used in the potassium-argon method of dating igneous rocks.

 MUSCOVITE

OCCURRENCE A common rock forming mineral, muscovite is found in igneous, metamorphic and detrital sedimentary rocks.  It is not usually valuable as a mineral specimen but can be found associated with other valued minerals such as tourmaline, topaz, beryl, almandine and others.

MINERAL DESCRIPTION Chemical formula : KAl2(AlSi3O10)(F,OH)2 MUSCOVITE was once commonly used for windows. The Russian mica mines that produced it gave muscovite its name (it was once widely known as "Muscovy glass"). Muscovite is a high-aluminium member of the mica family of minerals, all known for the property of perfect basal cleavage; cleavage layers can be easily peeled off into very thin sheets which are quite durable and are not easily destroyed by erosion.  Muscovite sheets have high heat and electrical insulating properties and are used to make electrical components.

OPTICAL PROPERTIES Colour : colourless Composition : highly variable Form : found as micaceous flakes or tablets with irregular outlines Twinning : rare Optic Orientation : parallel extinction, cleavage traces are length slow Alteration : not generally altered Distinguishing Features : colourless, parallel extinction, "birds-eye" extinction Bird's eye maple, or bird's eye extinction, is a specific type of extinction exhibited by minerals of the mica group under cross polarized light (sometimes called the optical analyser). It gives the mineral a pebbly appearance as it passes into extinction.

SYSTEM: MONOCLINIC Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

MUSCOVITE - PHYSICAL PROPERTIES Colour : colourless, yellow, brown, green, red Streak : white Lustre : vitreous Diaphaneity : transparent to translucent Cleavage : perfect Hardness : 2.5 – 3 Specific Gravity : 2.8 - 2.9 Chemical Classification : silicate

MUSCOVITE – USES Muscovite has a high resistance to heat and, split into thin transparent sheets, it has been used as windows on high- temperature furnaces and ovens. It is an insulator and was used in the past to make circuit boards. Historically, it was used as an early window glass.

CALCITE

CALCITE - DESCRIPTION Calcite is a rock-forming mineral with a chemical formula of CaCO3. It is extremely common and found throughout the world in sedimentary, metamorphic and igneous rocks. Calcite is the principal constituent of limestone and marble. These rocks are extremely common and make up a significant portion of Earth's crust. They serve as one of the largest carbon repositories on our planet.  

CALCITE - DESCRIPTION – CONTD. The properties of calcite make it one of the most widely used minerals. It is used as a construction material, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical and more. It has more uses than almost any other mineral. 

CRYSTAL SYSTEM  The true rhombohedral unit cell, which is the acute rhombohedra, and the cleavage rhombohedron setup. The true unit cell includes 2 CaCO3 with calcium ions at the corners of the rhombohedron and CO3 groups. Each of which consists of a carbon ion at the centre of a planar group of oxygen atoms whose centres define an equilateral triangle.

CALCITE – PHYSICAL PROPERTY Mineral class : Carbonates - Calcite group. Cleavage : Perfect rhomboedric in three planes, subconchoidal fracture. Hardness : 3 Density : 2.7 Colour : usually colourless, but nuances in blue, yellow, green, red, violet, even black and opaque. Streak : White to greyish. Lustre : Vitreous to pearly or dull.

USES OF CALCITE IN CONSTRUCTION The construction industry is the primary consumer of calcite in the form of limestone and marble. These rocks have been used as dimension stones and in mortar for thousands of years. Limestone blocks were the primary construction material used in many of the pyramids of Egypt and Latin America. Today, rough and polished limestone and marble are still an important material used in prestige architecture. 

USES OF CALCITE IN CONSTRUCTION – CONTD. Modern construction uses calcite in the form of limestone and marble to produce cement and concrete. These materials are easily mixed, transported and placed in the form of a slurry that will harden into a durable construction material. Concrete is used to make buildings, highways, bridges, walls .

OTHER USES OF CALCITE In a powdered form, calcite often has an extremely white colour. Powdered calcite is often used as a white pigment or "whiting". Some of the earliest paints were made with calcite. It is a primary ingredient in whitewash and it is used as an inert colouring ingredient of paint.  It is softer than the stone, porcelain and plastic surfaces found in kitchens and bathrooms but more durable than dried food and other debris that people want to remove . This is a non-flammable dust that is sprayed onto the walls and roofs of underground coal mines to reduce the amount of coal dust.

GYPSUM (CaSO4.2H2O) Gypsum- a soft sulphate mineral composed of calcium sulphate di hydrate. Gypsum was known in Old English as spærstān, "spear stone", referring to its crystalline projections. Dehydrated gypsum is popularly known as “plaster of Paris”. Gypsum crystals contain anion water and hydrogen bonding.

PROPERTIES Category Colour Cleavage Mohs scale Lustre Specific gravity Solubility -Sulphate minerals -White, colorless. May be pink, brown, red due to impurities. -Perfect on 010 distinct on 100 -1.5-2 -Vitreous to silky, pearly or waxy. -2.31 to 2.33 -Hot, dilute Hcl

GYPSUM CRYSTALS

APPLICATIONS Used as cement blocks in building. An ancient mortar used in building construction. Binder in fast-dry tennis courts. Fertilizer and soil conditioner.

CLAY

Clay- a fine grained soil. Distinguished from other soil by size. Formed by gradual weathering of rocks. Absorb or lose water depending on humidity changes. Due to absorption of water, specific gravity of clay is variable. Divided into kaolinite, illite, vermiculite, smectite and chlorite.

PRODUCTION

USES Used in pottery, decorative and construction products. Macaws use clay licks for survival. Can soothe an upset stomach. Primary ingredient in building techniques. Kaolin clay – used as anti-diarrheal medicines. Removal of heavy metals from waste water.

PROPERTIES QUARTZ FELSPAR GROUP MUSCOVITE BIOTITE MICA GYPSUM CRYSTAL SYSTEM Hexagonal Monoclinic and Triclinic Monoclinic Category of sulphate COLOUR Colourless when pure; red, green, blue Grey, green, blue, pink and white White to Colourless Greenish to brown or black; even yellow White, yellowish, green, grey White, colourless HARDNESS 7 6 – 6.5 2 – 2.5 2.5 - 3 1.5 - 2 SPECIFIC GRAVITY 2.65 – 2.66 2.54 – 2.57 2.76 - 3 2.7 – 3.1 2.8 2.31 – 2.33 CLEAVAGE Generally absent Perfect Highly perfect basal cleavage LUSTRE Vitreous

PROPERTIES AMPHIBOLE MINERALS CALCITE CRYSTAL SYSTEM Monoclinic Crystalline, granular, rhombohedra COLOUR White to light grey White or colourless; also grey, yellow & green HARDNESS 5.5 – 6 3 SPECIFIC GRAVITY 2.9 - 3 2.71 CLEAVAGE Perfect Perfect with 74’ LUSTRE Vitreous