MINEROLOGY

1. MINEROLOGY Acknowledging Monika, Syed, Priyanka, Nitin, SaiPradeep and Srivatsan

2. CONTENTS UNIT II MINEROLOGY Physical properties of minerals – Quartz group, Feldspar group, Pyroxene – hypersthene and augite, Amphibole – hornblende, Mica – muscovite and biotite, Calcite, Gypsum and clay minerals Sivapriya Vijayasimhan

3. quartz Sivapriya Vijayasimhan

4. 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 : Α quartz, β quartz. Identification of the exact type of quartz (into Αand β) requires thorough 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 in distinct crystals ,quartz may be distinguished into right handed and left handed types. This is done 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. Sivapriya Vijayasimhan

5. 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. Sivapriya Vijayasimhan

6. 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 orthoquartzites. 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. Sivapriya Vijayasimhan

7. PIEZOELECTRICITY 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 Sivapriya Vijayasimhan

8. AMETHYSTINE QUARTZCITRINES Sivapriya Vijayasimhan

9. Felspar group The feldspars are the most prominent group of minerals making more than fifty percent , by weight ,crust of the earth up to a depth of 30 km. These occur chiefly in the igneous rocks(more than 60 percent) but also form a good portion of their metamorphic derivatives. Felspars are also found in some sedimentary rocks like arkose and greywacks. The group comprises about a dozen or so minerals of which 3-4 may be easily described as the most common minerals in rocks. CHEMICAL COMPOSITION In chemical constitution , felspars are chiefly aluminosilicates of sodium , potassium and calcium with the following general formula : WZ4O8 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 Sivapriya Vijayasimhan

10. ATOMIC STRUCRURE • At atomic level ,the felspars shows a continuous three- dimensional network type of structure in which SiO4tetrahedra are linked at all the corners, each oxygen ion being shared by two adjacent tetrahedra. • The SiO4tetrahedra is accompanied by AlO4tetrahedra so that the felspar 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 felspar 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 felspar: These are also called the plagioclase felsparsand 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. Sivapriya Vijayasimhan

11. Crystallographically ,felspar fall in two crystal systems . Monoclinic Felspars 1. Orthoclase (KAlSi3O8 ) 2. Sanidine (KAlSi3O8 ) Triclinic Felspars 1. Microcline (KAlSi3O8 ) Albite – Anorthite series(six minerals)es(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. They are generally light in colour, have lower specific gravity ,have a double cleavage and a hardness varying between 6-6.5. Among the felspar group, the following mineral species are quite common as rock forming minerals and hence are described in detail. Orthoclase Microcline Albite Anorthite Sivapriya Vijayasimhan

12. Orthoclase Sivapriya Vijayasimhan

13. microcline Sivapriya Vijayasimhan

14. albite

15. anorthite

16. 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 Sivapriya Vijayasimhan

17. CrystallizationCrystals – long, slender, prismatic, sometimes fibrousPrism angle – 124’ AMPHIBOLE MINERALS ORTHORHOMBIC MONOCLINIC Sivapriya Vijayasimhan

18. PHYSICAL PROPERTIES 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 Sivapriya Vijayasimhan

19. Monoclinic Amphiboles TREMOLITE Ca2Mg5 [(Si4O11)]2 [OH]2

20. ACTINOLITE Ca2 (Mg, Fe)5 [(Si4O11)]2 [OH]2

21. AUGITE

22. 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. Augiteusually 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.

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

24. 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°.

25. Augite – Physical Properties Color : 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. Luster : vitreous Diaphaneity : translucent to opaque Cleavage : prismatic Hardness : 5.5 – 6 Specific Gravity : 3.2 - 3.6 DistinguishingCharacteristics : two cleavage directions almost at right angles, dark green to black color Chemical Classification : silicate

26. 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.

27. Hornblende

28. 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 amphibolites.

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

30. 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

31. Physical Properties Color : dark green to black. Streak : gray to greenish gray Luster : vitreous Diaphaneity : translucent to nearly opaque Cleavage : good Hardness :5.0 - 6.0 Specific Gravity : 3.0 - 3.5

32. 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.

33. BIOTITE

34. Description of Biotite General Formula:K2(Mg,Fe)3AlSi3O10(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.

35. 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 color 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. The localities listed below highlight typical or remarkable biotite occurrences in the state.

36. 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

37. System:Monoclinc • Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

38. Biotite - Physical Properties Color: black, dark green, dark brown Streak: white to gray. Luster: vitreous. Diaphaneity: transparent to translucent. Cleavage: basal, perfect Hardness: 2.5 – 3 Specific Gravity: 2.7 - 3.3 Chemical Classification: silicate

39. Biotite - uses Biotite has very limited commercial use. Biotiteparticles 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.

40. Muscovite

41. 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 is a high-aluminum 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.

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

43. 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 analyzer). It gives themineral a pebbly appearance as it passes into extinction.

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

45. Muscovite - Physical Properties Color : colorless, yellow, brown, green, red Streak : white Luster : vitreous Diaphaneity : transparent to translucent Cleavage : perfect Hardness : 2.5 – 3 Specific Gravity : 2.8 - 2.9 Chemical Classification : silicate

46. 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.

47. Calcite

48. 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 igneousrocks. 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.  

49. 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. 

50. Crystal System • The true rhombohedralunit cell, which is the acute rhombohedron, and the cleavage rhombohedron setup. • The true unit cell includes 2 CaCO3 with calcium ions at the corners of the rhombohedrons and CO3groups. • Each of which consists of a carbon ion at the centre of a planar group of oxygen atoms whose centres define an equilateral triangle.