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A. IDENTIFICATION OF FORMING group:

Sl. Physical Specimen No. Specimen No. Specimen No. No. Properties 1 Habit/Form Crystalline Crystalline Massive 2 Colour Colourless Purple, Violet Grey 3 Colourless Colourless Colourless 4 Lustre Vitreous Vitreous Vitreous 5 Absent Absent Absent 6 Conchoidal/Subconchoidal Conchoidal/Subconchoidal Conchoidal/Subconchoidal 7 Hardness 7 7 7 8 Specific 2.65 (Medium) 2.65 (Medium) 2.65 (Medium) gravity 9 Diaphinity Transparent/Translucent Transparent/Translucent Translucent 10 Diagnostic Absence of Cleavage, Absence of Cleavage, Absence of Cleavage, properties habit, hardness and fracture colour, hardness and colour, hardness and fracture fracture 11 Rock Grey Quartz Name 12 Chemical SiO2 SiO2 SiO2 composition 13 Occurrence Acidic Igneous rocks Acidic Igneous rocks Acidic Igneous rocks (Granite, Rhyolite, (Granite, Rhyolite, (Granite, Rhyolite, Pegmatite), Sedimentary Pegmatite), Sedimentary Pegmatite), Sedimentary rocks (Sandstone), rocks (Sandstone), rocks (Sandstone), metamorphic rocks metamorphic rocks metamorphic rocks (Quartzite) and (Quartzite) and (Quartzite) and hydrothermal rocks. Some hydrothermal rocks. Some hydrothermal rocks. times as cavity fillings. times as cavity fillings. 14 Uses Glass, ceramics, Glass, ceramics, Glass, ceramics, refractories, flux, refractories, flux, refractories, flux, piezoelectrics, ornamental piezoelectrics, ornamental piezoelectrics, ornamental and semiprecious stones. and semiprecious stones. and semiprecious stones.

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Quartz group contd…..

Sl. Physical Specimen No. Specimen No. Specimen No. No. Properties 1 Habit/Form Massive Massive Massive 2 Colour Rose, Pink Milky white Greenish ground mass with blood red spots 3 Streak Colourless Colourless Colourless 4 Lustre Vitreous Vitreous Resinous 5 Cleavage Absent Absent Absent 6 Fracture Conchoidal/Subconchoidal Conchoidal/Subconchoidal Conchoidal/Subconchoida l 7 Hardness 7 7 7 8 Specific 2.65 (Medium) 2.65 (Medium) 2.65 (Medium) gravity 9 Diaphinity Translucent Translucent Opaque 10 Diagnostic Absence of Cleavage, Absence of Cleavage, Absence of Cleavage, properties colour, hardness and colour, hardness and colour, hardness and fracture fracture fracture 11 Mineral Name Rosy Quartz Milky Quartz Blood stone 12 Chemical SiO2 SiO2 SiO2 composition 13 Occurrence Acidic Igneous rocks Acidic Igneous rocks Acidic Igneous rocks (Granite, Rhyolite, (Granite, Rhyolite, (Granite, Rhyolite, Pegmatite), Sedimentary Pegmatite), Sedimentary Pegmatite), Sedimentary rocks (Sandstone), rocks (Sandstone), rocks (Sandstone), metamorphic rocks metamorphic rocks metamorphic rocks (Quartzite) and (Quartzite) and (Quartzite) and hydrothermal rocks hydrothermal rocks hydrothermal rocks 14 Uses Glass, ceramics, Glass, ceramics, Glass, ceramics, refractories, flux, refractories, flux, refractories, flux, piezoelectrics, ornamental piezoelectrics, ornamental piezoelectrics, ornamental and semiprecious stones. and semiprecious stones. and semiprecious stones.

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Quartz group contd…..

Sl. Physical Specimen No. Specimen No. Specimen No. No. Properties 1 Habit/Form Massive Massive Banded 2 Colour Pale grey Light grey to brown Pale blue, grey 3 Streak Colourless Colourless Colourless 4 Lustre Resinous to dull Resinous Resinous 5 Cleavage Absent Absent Absent 6 Fracture Subconchoidal Conchoidal/Subconchoidal Conchoidal/Subconchoidal 7 Hardness 7 7 7 8 Specific 2.65 (Medium) 2.65 (Medium) 2.65 (Medium) gravity 9 Diaphinity Opaque Translucent to opaque Translucent 10 Diagnostic Absence of Cleavage, Absence of Cleavage, Absence of Cleavage, properties hardness and conchoidal hardness and fracture hardness and fracture fracture 11 Mineral Flint Name 12 Chemical SiO2 SiO2 SiO2 composition 13 Occurrence Acidic Igneous rocks Acidic Igneous rocks Acidic Igneous rocks (Granite, (Granite, Rhyolite, (Granite, Rhyolite, Rhyolite, Pegmatite), Pegmatite), Sedimentary Pegmatite), Sedimentary Sedimentary rocks rocks (Sandstone), rocks (Sandstone), (Sandstone), metamorphic metamorphic rocks metamorphic rocks rocks (Quartzite) and (Quartzite) and (Quartzite) and hydrothermal rocks hydrothermal rocks hydrothermal rocks 14 Uses Glass, ceramics, Glass, ceramics, Glass, ceramics, refractories, refractories, flux, refractories, flux, flux, piezoelectrics, piezoelectrics, piezoelectrics, ornamental ornamental and semiprecious ornamental and and semiprecious stones. stones. semiprecious stones.

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Quartz group contd….

Sl. Physical Specimen No. Specimen No. Specimen No. No. Properties 1 Habit/Form Massive/banded Massive Amorphous 2 Colour Grey, pale brown, pale Red White pink 3 Streak Colourless Colourless Colourless 4 Lustre Resinous Resinous to dull Resinous 5 Cleavage Absent Absent Absent 6 Fracture Conchoidal/Subconchoidal Conchoidal Conchoidal/Subconchoidal 7 Hardness 7 7 7 8 Specific gravity 2.65 (Medium) 2.65 (Medium) 2.0-2.2 (Low) 9 Diaphinity Translucent to opaque Translucent to opaque Translucent to opaque 10 Diagnostic Absence of Cleavage, Absence of Cleavage, Absence of Cleavage, properties hardness and conchoidal colour, hardness and amorphous habit, hardness fracture conchoidal fracture and conchoidal fracture 11 Mineral Name Chert 12 Chemical SiO2 SiO2 SiO2 nH2O composition 13 Occurrence Acidic Igneous rocks Acidic Igneous rocks Acidic Igneous rocks (Granite, Rhyolite, (Granite, Rhyolite, (Granite, Rhyolite, Pegmatite), Sedimentary Pegmatite), Sedimentary Pegmatite), Sedimentary rocks (Sandstone), rocks (Sandstone), rocks (Sandstone), metamorphic rocks metamorphic rocks metamorphic rocks (Quartzite) and (Quartzite) and (Quartzite) and hydrothermal rocks hydrothermal rocks hydrothermal rocks 14 Uses Glass, ceramics, Glass, ceramics, Glass, ceramics, refractories, flux, refractories, flux, refractories, flux, piezoelectrics, ornamental piezoelectrics, ornamental piezoelectrics, ornamental and semiprecious stones. and semiprecious stones. and semiprecious stones.

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Feldspar group: Sl. Physical Properties Specimen No. Specimen No. Specimen No. No. 1 Habit/Form Tabular Tabular Tabular 2 Colour Flesh red Green Grey, white 3 Streak Colourless Colourless Colourless 4 Lustre Vitreous Vitreous Vitreous 5 Cleavage 2 sets, perfect 2 sets, perfect 2 sets, perfect 6 Fracture Subconcoidal/Uneven Subconcoidal/Uneven Subconcoidal/Uneven 7 Hardness 6 6 6 8 Specific gravity 2.56 (Medium) 2.56 (Medium) 2.62-2.76 (Medium) 9 Diaphinity Translucent to opaque Translucent to opaque Translucent to opaque 10 Diagnostic properties Colour, hardness, Colour, hardness, Hardness, tabular habit tabular habit and tabular habit and and presence of 2 sets presence of 2 sets of presence of 2 sets of of cleavages cleavages cleavages 11 Mineral Name 12 Chemical KAlSi3O8 KAlSi3O8 NaAlSi3O8-CaAl2Si2O8 composition 13 Occurrence In acid and partially In acid and partially In acid and partially intermediate igneous intermediate igneous intermediate igneous rocks like Granite, rocks like Granite, rocks like Granite, Syenite, Felsites, Syenite, Felsites, Syenite, Felsites, Rhyolite Rhyolite and in Rhyolite pegmatites and alkali rocks 14 Uses Opalescent glass, Opalescent glass, Opalescent glass, porcelain, enamel, porcelain, enamel, porcelain, enamel, ceramics, ornamental ceramics, ornamental ceramics, ornamental and semiprecious and semiprecious and semiprecious stones. stones. stones.

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Mica group:

Sl. No. Physical Properties Specimen No. Specimen No. 1 Habit/Form Foliated, flaky Foliated, flaky 2 Colour Colourless Black, brown 3 Streak White White to grey 4 Lustre Pearly Pearly 5 Cleavage Basal perfect (1 set) Basal perfect (1 set) 6 Fracture Uneven Uneven 7 Hardness 2.5 2.5 8 Specific gravity 2.8-2.9 (Medium) 2.8-3.4 (Medium) 9 Diaphinity Transparent Transparent to translucent 10 Diagnostic Habit, colour, luster, basal cleavage Habit, colour, luster, basal cleavage properties 11 Mineral Name 12 Chemical KAl2(AlSi3O10)(OH,F)2 K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2 composition 13 Occurrence Intrusives ; greisens, pegmatites, Magmatic; in pegmatites, contact hydrothermalites, metamorphosed metasomatic, metamorphic rocks rocks (Schists) (Schists) 14 Uses Electrical industry for condenser, as Electrical industry for condenser, as insulating material b/w commutator insulating material b/w commutator segments and in heating elements segments and in heating elements

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Carbonate group:

Sl. Physical Specimen No. Specimen No. Specimen No. No. Properties 1 Habit/Form Tabular, Crystalline Tabular, Crystalline Massive 2 Colour White Grey White 3 Streak White White White 4 Lustre Vitreous Vitreous Dull to earthy 5 Cleavage Perfect (3 sets) Perfect (3 sets) Perfect 6 Fracture Subconchoidal/Uneven Subconchoidal/Uneven Subconchoidal/Uneven 7 Hardness 3 3.5-4 3.5-4.5 8 Specific 2.71 (Medium) 2.85 (Medium) 2.8-3 (Medium) gravity 9 Diaphinity Transparent to Translucent Opaque translucent 10 Diagnostic Double refraction, Slightly attacked by Scarcely affected by properties effervesces freely in cool, dilute HCl, cold HCl but gives cold dilute HCl, elephant skin effervescence in hot hardness and weathering, grey colour HCl, compact massive Rhombohedral and Rhombohedral habit, hardness cleavages cleavages 11 Mineral Name 12 Chemical CaCO3 CaMg(CO3)2 MgCO3 composition 13 Occurrence Limestone, Marble, Transformation of Occurs rarely as altered basic igneous sedimentary CaCO3 by sedimentary rock. rocks magnesium bearing Alteration of rocks that solutions, rarely consist largely of hydrothermal magnesium silicate by carbonate water, commonly associated with -chlorite or schist 14 Uses Optical accessories, Extract Ca, Mg metal, Refractory bricks, cement, chemical refractory bricks, as flux cement and flooring , industry and as in blast furnace extract Mg metal fertilizer

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Olivine group: group:

Sl. No. Physical Specimen No. Sl. Physical Specimen No. Properties No. Properties 1 Habit/Form Granular 1 Habit/Form Crystalline 2 Colour Olive green 2 Colour Brownish red 3 Streak Colourless 3 Streak Colourless 4 Lustre Vitreous to sub-vitreous 4 Lustre Vitreous 5 Cleavage Poor 5 Cleavage None 6 Fracture Uneven 6 Fracture Uneven 7 Hardness 6-7 7 Hardness 6.5-7.5 8 Specific 3.2-3.5 (Medium) 8 Specific gravity 3.5-4.3 (High) gravity 9 Diaphinity Translucent to opaque 9 Diaphinity Translucent to opaque 10 Diagnostic Habit, Colour, higher 10 Diagnostic Olive green colour, properties Hardness and specific properties granular habit gravity 11 Mineral Name 11 Mineral Name Garnet 12 Chemical (Fe, Mg)2SiO4 12 Chemical Silicate of Ca, Mg, Fe, composition composition Mn, Cr, Al 13 Occurrence Important constituent of 13 Occurrence Metamorphic rocks like ultramafic rocks like gneisses and schists and Dunite, Peridotite rarely in igneous rocks 14 Uses Refractories, like granite and and ornamental stone pegmatite 14 Uses Gemstone, ornamental stone, abrasive

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Amphibole group:

Sl. Physical Specimen No. Specimen No. No. Properties 1 Habit/Form Bladed Fibrous 2 Colour Green Grey 3 Streak Pale green Light grey 4 Lustre Vitreous Silky 5 Cleavage Perfect (2 sets) Present 6 Fracture Uneven Uneven 7 Hardness 5.5-6 3 8 Specific gravity 3.1-3.3 (Medium) 3 (Medium) 9 Diaphinity Translucent to opaque Opaque 10 Diagnostic Colour, habit, vitreous Fibrous habit, silky lustre properties lustre, cleavage angle 1240

11 Mineral Name 12 Chemical (Ca, Mg, Fe, Na, Al)7-8 Complex silicate of Fe, composition (Al,Si)8O22(OH)2 Mg, Ca and Al 13 Occurrence In intermediate intrusive It is formed as a rocks, alkali extrusive and retrograde hydrothermal metamorphic rocks alteration of ultrabasic rocks like Peridotite. 14 Uses Rarely as gemstone and Fire proof materials, precious stone insulators, lubricants, asbestos sheets, board and paints

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Clay mineral: Sulphate group:

Sl. Physical Specimen No. Sl. Physical Specimen No. No. Properties No. Properties 1 Habit/Form Massive 1 Habit/Form Platy 2 Colour White 2 Colour White 3 Streak White 3 Streak White 4 Lustre Earthy 4 Lustre Vitreous to sub vitreous 5 Cleavage Perfect 5 Cleavage Perfect (1 set) 6 Fracture Uneven 6 Fracture Subconchoidal to 7 Hardness 1.5 uneven 8 Specific gravity 2.6 (Medium) 7 Hardness 2 9 Diaphinity Opaque 8 Specific gravity 2.3 (Medium) 10 Diagnostic Colour, earthy lustre and 9 Diaphinity Translucent properties hardness 10 Diagnostic Hardness, cleavage, 11 Mineral Name Kaolin properties Habit 12 Chemical Al4Si4O10(OH)8 11 Mineral Name composition 12 Chemical CaSO4. 2H2O 13 Occurrence Primary residual composition deposits formed by 13 Occurrence As saline residue, weathering of low accompanying the temperature dolomitization of hydrothermal alteration limestone in the sea. In of and other Al- zone of oxidation of rich silicates usually in sulphides acidic rocks like granite 14 Uses Fertilizers, fillers, 14 Uses Ceramic, textile, acid plaster of Paris, optical refractory bricks, accessories foundry sand, paints

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Oxides: Other silicates:

Sl. Physical Specimen No. Sl. Physical Specimen No. No. Properties No. Properties 1 Habit/Form Barrel shaped 1 Habit/Form Massive 2 Colour Brown 2 Colour White 3 Streak Colourless 3 Streak White 4 Lustre Vitreous 4 Lustre Pearly 5 Cleavage Poor 5 Cleavage Perfect 6 Fracture Subconchoidal to 6 Fracture Uneven uneven 7 Hardness 1 7 Hardness 9 8 Specific gravity 2.7-2.8 (Medium) 8 Specific gravity 4.02 (High) 9 Diaphinity Translucent 9 Diaphinity Opaque 10 Diagnostic Soapy or greasy feel and 10 Diagnostic Hardness, barrel shape properties hardness properties 11 Mineral Name Talc 11 Mineral Name 12 Chemical Mg3(Si2O10)(OH)2 12 Chemical Al2O3 composition composition 13 Occurrence Occurs as secondary mineral 13 Occurrence Silica deficient rocks resulting from the hydration like syenite, pegmatite, of magnesium bearing rocks, contact metamorphism such as peridotites, gabbro, of highly aluminous dolomites etc, and also in talc rocks schist 14 Uses Abrasive, gemstone and 14 Uses Fillers, Talcum powder, ornamental stone paints, lubricants

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B. IDENTIFICATION OF ORE FORMING MINERALS

Oxides and hydroxides:

Sl. Physical Specimen No. Specimen No. Specimen No. No. Properties 1 Habit/Form Crystalline Banded Massive 2 Colour Metallic black Metallic black Reddish brown 3 Streak Black Cherry red Pale reddish brown 4 Lustre Metallic Metallic Sub metallic to dull 5 Cleavage None Poor None 6 Fracture Uneven Uneven Uneven 7 Hardness 6 5.5-6.5 5 8 Specific gravity 5.15 (High) 5.26 (High) 3.6-4 (High) 9 Diaphinity Opaque Opaque Opaque 10 Diagnostic Magnetic property and Cherry red streak Yellow to reddish brown properties black streak colour and streak 11 Mineral Name (Banded Hematite Jasper) 12 Chemical Fe3O4 Fe2O3 FeO(OH)n,H2O composition 13 Occurrence As magmatic segregation, As sedimentary, As an alteration product contact-metamorphic and magmatic, contact- of rocks containing iron hydrothermal deposits metamorphic and bearing minerals, hydrothermal biogenic precipitate in deposits swamps and found in gossans 14 Uses Ore of Iron, manufacture Ore of Iron, Ore of Iron, paints and of steel manufacture of pigments steel

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Oxides and hydroxides contd….

Sl. No. Physical Specimen No. Specimen No. Specimen No. Specimen No. Properties 1 Habit/Form Granular Acicular Massive Pisolitic 2 Colour Metallic black Metallic black Metallic black Dirty white, brown, yellow, reddish brown 3 Streak Dark brown Black Brownish black Yellow to brown 4 Lustre Sub metallic Metallic Sub metallic Dull 5 Cleavage None Perfect None None 6 Fracture Uneven Uneven Uneven Uneven 7 Hardness 5.5 2-2.5 5-6 2-4 8 Specific gravity 4.6 (High) 4.75 (High) 3.7-4.7 (High) 2-3.5 (Medium) 9 Diaphinity Opaque Opaque Opaque Opaque 10 Diagnostic Metallic black Acicular habit, Brownish black Pisolitic habit, colour, properties colour and dark black streak and streak and dull lustre brown streak low hardness association with 11 Mineral Name Pyrolusite Bauxite 12 Chemical FeCr2O4 MnO2 (Ba,H2O)2Mn5O10 Al2O32H2O composition 13 Occurrence Primary mineral Alteration of Alteration of As a secondary of ultrabasic product of rocks product of rocks product, commonly igneous rocks, containing containing formed under peridotites, manganese bearing manganese subtropical to tropical serpentinites, minerals, as bearing minerals, climatic conditions by basic gabbros residual or lateritic as residual or the leaching away of deposits lateritic deposits, silica from aluminium colloidal bearing rocks. precipitate 14 Uses Ore of Ore of Manganese Ore of Ore of Aluminium, as , used Manganese refractory and in plating, abrasive material manufacture of steel

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Sulphides:

Sl. No. Physical Properties Specimen No. Specimen No. Specimen No.

1 Habit/Form Massive, Striated cubes Massive Cubic crystal

2 Colour Brass yellow Golden yellow Lead grey

3 Streak Greenish or brownish Greenish black Greyish black

black

4 Lustre Metallic Metallic Metallic 5 Cleavage Present (3 sets) Imperfect Present (3 sets) 6 Fracture Uneven Uneven Uneven 7 Hardness 6-6.5 3.5-4 2.5 8 Specific gravity 4.8-5.1 (High) 4.1-4.3 (High) 7.4-7.6 (High) 9 Diaphinity Opaque Opaque Opaque 10 Diagnostic Cubic , brass Brass yellow High specific properties yellow colour and colour and gravity, cubic form greenish or brownish greenish black and cleavage, lead black streak streak grey colour 11 Mineral Name 12 Chemical FeS2 CuFeS2 PbS composition 13 Occurrence As an accessory mineral Magmatic, An important in igneous rocks, hydrothermal, less hydrothermal common constituent of frequently deposit, contact many ore-veins, exogenic metamorphic magmatic segregation, deposit and as contact metamorphic or disseminations in pyrometasomatic sedimentary rocks 14 Uses Extraction of Ore of Copper Ore of Lead, commercial sulphur, storage batteries, manufacture of sulfuric glass glazing, paint acid and alloys

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Mineral: A mineral is a naturally occurring homogenous inorganic substance, having a definite range of chemical composition, definite internal atomic structure and external form.

Minerals are broadly grouped into two types namely rock forming minerals and ore forming minerals. Rock forming minerals are those minerals which are abundantly found in rocks (example: quartz, feldspar, mica, amphiboles, pyroxenes etc.), whereas ore forming minerals are those minerals from which we can extract metals economically (example: Haematite, Magnetite, Limonite, from which we can extract iron metal).

Distinguish between rock forming and ore forming minerals Rock forming minerals Ore forming minerals 1. Abundantly present in rocks Extract more than one metal economically Example: Quartz group, feldspar group, mica group etc. Example: Magnetite, Haematite, Bauxite etc., 2. Shows non-metallic lustre(Vitreous, Resinous, pearly etc.,) Shows metallic lustre 3. Shows conchoidal/sub-conchoidal/even/uneven fracture Shows uneven fracture 4. Shows medium specific gravity Shows high Specific gravity 5. Shows transparent/translucent/opaque diaphinity Shows opaque diaphinity

Physical properties of minerals: A set of properties which are always distinctive related to the body of a mineral (example: colour, hardness, shape etc.) are aptly termed as physical properties. The study of physical properties of minerals is important, since it varies from mineral to mineral. Physical properties depending upon light: Colour:The colour shown by a mineral depends upon the absorption of some and the reflection of others of the coloured rays or vibration composing the ordinary white light. When a mineral absorbs all the vibrations of the different colours, it appears black. But when it reflects all the vibrations of the different colours, it appears white. If a mineral reflects the red vibrations and absorbs all other vibrations, it appears red colour. The colour of the mineral is often its most striking property. Some minerals shows distinctive colour and are as follows: White: Calcite, , Magnesite, Talc, Opal Blue: , Green: , , Microcline, Chlorite Yellow: Sulphur, Chalcopyrite, Pyrite Red: Jasper, Orthoclase, Garnet Lead grey: Galena, Steel grey: Haematite. The variations of colour in minerals may be due to: a. Surface alterations b. Difference in chemical composition c. Presence of impurities d. Inclusions of some other mineral matters etc., Play of colours: On rapidly turning a mineral, a change of several colours may occur in rapid succession. This

is caused by reflection of light from within the mineral. Example: .

Change of colours: The colour of mineral changes as it is slowly turned. This is caused by differences in the 1

reflection of light from the surface of the mineral. Example: Tigers eye. Page

Iridescence: Iridescence is a display of rainbow or prismatic colours due to the interference of rays of light in minute fissures containing thin film of air or liquid. It is also related to reflections from the inclusions. Example: Limonite, Calcite Opalescence: A milky or pearly reflection from the interior of a specimen. Example: Opal Fluorescence: A few minerals have the property of glowing or emitting light when they are exposed to ultra violet light orx-rays, or cathode rays are called florescence. Example: . If the emission of light continues after the light is cut off, they are said to be phosphorescent. Example: some Calcite. Streak: Streakis the colour of the powder of the mineral and may be obtained by rubbing the fresh mineral surface on an unglazed porcelain plate called “Streak Plate”. The streak may be of different colours from the mineral colour. Examples: Mineral Colour Streak Galena Steel grey Lead grey Haematite Metallic black Cherry red Chalcopyrite Brass yellow Greenish black Lustre: The appearance of the shining surface of a mineral in reflected light is called lustre. The intensity of lustre is depending upon the amount and type of reflection of light that take place at their surfaces. There are several kinds of lustre, among them being the following; 1. Metallic: The ordinary lustre of metals. Example: Galena, Pyrite etc., 2. Vitreous: The lustre of broken glass. Example: Quartz, Feldspar 3. Resinous: The lustre of resin or wax. Example: Agate, Opal 4. Pearly: The lustre of a . Example: Biotite, Muscovite etc., 5. Silky: The lustre of silk. Example: Asbestos, Satinspar etc., 6. Adamantine: The lustre of . Example: Diamond, Corundum etc., Diaphinity: Diaphinity is the ability of a mineral to transmit light. There are three types of diaphinities as follows; Transparent: Minerals capable of transmitting light and through which an outlines of objects can be seen clearly. Example: Rock crystal, Muscovite etc., Translucent: Minerals capable of transmitting only a part of light and through which an outlines of objects cannot be seen clearly. Example: Chalcedony, Agate etc., Opaque: Minerals that are incapable of transmitting light and the objects are not seen though it. Example: Magnetite, Haematite etc.,

Physical properties depending upon state of aggregation: Crystal Form:Under favorable conditions minerals assume a definite crystal form. In such an environment the minerals develop as crystals with regular pattern of faces and angles between adjoining faces.The following descriptive terms are used to describe the crystal forms.

Crystallized: A term denoting that the mineral occurs as well developed crystals. Crystalline: A term denoting that no definite crystals are developed, but an aggregate of imperfect crystal grains have formed, interfering with one another during their growth. Amorphous: A term used to describe the complete absence of crystalline structure.

Habit:If crystals grow into one another or in a restricted environment, it is possible that no well-formed 2

crystal faces will be developed. However, crystals sometimes develop certain forms more commonly than Page others, although the symmetry may not be readily apparent from these common forms. The term used to describe general shape of a crystal is habit.

Some common crystal habits are as follow; Acicular – fine needle like crystals. Example: Amygdaloidal – almond shaped aggregates. Example: Zeolites Bladed – shaped like a knife blade or a lath. Example: Botryoidal – Consisting of spheroidal aggregations, resembles like bunch of graphs. Example: Chalcedony. Columnar – aggregates making slender columns. Example: Beryl Dentritic – branching like trees, twigs. Example: Pyralusite Fibrous – consisting of fine hair or thread like strands. Example: Asbestos Foliated – consisting of thin and separable lamellae or leaves. Example: Mica Granular – even sized coarse or fine grained aggregates. Example: Olivine Radiating – needles or fibers arranged around a central point. Example: Reniform – kidney shaped. Example: Haematite Tabular – showing broad flat surfaces. Example: Prismatic – elongated crystals in one direction. Example: Calcite Oolitic – consisting of small spheroids or ellipsoids that resemble fish eggs. Example: Haematite Pisolitic – similar to oolitic but spheroids are larger in size. Example: Bauxite Drusy or cavity filling – small or large crystals having the walls of cavities or projecting from an amorphous or banded base. Example: Amethyst Massive – irregular structure. Example: Magnesite Nodular – Smooth rounded or irregular masses like river gravel/pebble. Example: Flint Hardness: Hardness may be defined as the resistance offered by the mineral to scratching or rubbing. The degree of hardness is determined by observing the comparative easy or difficulty in scratching it with another mineral of known hardness or by a penknife. For example, the mineral scratches orthoclase feldspar but does not scratch quartz means it has hardness between 6 and 7. The German mineralogist Fredrich Mohs arranged ten common minerals in order of increasing hardness and assigned each of the reference minerals a number. This series is commonly known as “Moh’s scale of hardness and is as follows. Table.1: Moh’s Scale of Hardness. Moh’s standard mineral Hardness Scratchability Talc 1 Can be scratched by finger nail very easily Gypsum 2 Can be scratched by finger nail with some difficulty Calcite 3 Can be scratched by copper coin Fluorite 4 Can be scratched by an iron nail 5 Can be scratched by an window glass Orthoclase 6 Can be scratched by an steel pocket knife Quartz 7 Can be scratched by an pen knife 8 Cannot be scratched by pen knife Corundum 9 Cannot be scratched by pen knife Diamond 10 Can be scratched by another diamond only By memorize the sentence “The God Can Feed An Orphan Quicker ThanCreature Done”, the above table can remember easily.

Cleavage: The tendency of certain minerals to break along a particular plane when under stress is called

as cleavage. Cleavage surfaces are always parallel to crystal faces of the mineral. The quality of a cleavage can 3 Page be described as perfect, good, distinct, poor,indistinct and none. Based on number of cleavage directions, cleavages are classified into several groups as follows; Basal cleavage: Good cleavage in one direction. Example: Muscovite, Biotite Prismatic cleavage: Cleavage in two directions not at right angles to each other. Example: Amphiboles Cubical cleavage: Cleavage in three directions at right angles to each other. Example: , Galena Rhombohedral cleavage: Cleavage in three directions not at right angle to each other. Example: Calcite. Octahedral cleavage: Cleavage in four directions. The cleavage planes are parallel to the octahedral faces. Example: Fluorite Dodecahedral cleavage: Cleavage in six directions. Example: .

Fracture: The nature of the broken surface of the mineral other than the direction of cleavage is called fracture. There are several types of factures as follows; Conchoidal: The broken mineral surface shows curved, concave or convex concentric rings. Example: Quartz. Sub conchoidal: A lesser degree of curved, concave or convex concentric rings. Example: Feldspars. Even: When mineral breaks with a smooth and regular flat surface. Example: Chert. Uneven: when mineral breaks with a rough and irregular surface. Example: Magnesite Hackly: When mineral breaks with irregular surface with sharp and jagged elevations. Example: .

Tenacity: Tenacity is the resistance that a mineral offered to mechanical deformation or disintegration when the mineral is submitted to bending, breaking crushing or cutting. There are different types of tenacities as follows; Brittle: Minerals which breaks or powders easily when struck with a hammer or cut by a knife instead of yielding a slice. Most minerals exhibit this property in some degree. Example: , fluorite Sectile: Minerals can be cut into thin shavings or slices with a knife. Example: Gypsum, steatite Malleable: Minerals which can be hammered into thin sheets. Example: Native copper, gold, silver. Ductile: Minerals which can be drawn into a wire. Example: Native copper, gold, silver. Flexible: A mineral that bends but does not resume its original shape when the pressure is released. Example: , Talc. Elastic: A mineral that after being bent will resume its original position upon the release of pressure. Example: Muscovite, Biotite.

Specific gravity: The specific gravity of a mineral is the ratio of the weight of the mineral to the weight of an equal volume of water at 40 C. Specific gravity of a mineral depends upon their chemical composition and molecular weight. Various scientific methods have been used to determine the specific gravity. The most practical methods used are Jolly’s spring balance, Beam balance, Walkers steel yard, pycnometer or specific gravity bottle, heavy liquids etc., depend upon the size and nature of the minerals. Specific gravity can be roughly estimated by using the relative terms as Low (2.5 and less); Less weight. Example: Graphite Medium (2.5 and 3.5); Medium weight. Example: Quartz, feldspar, calcite High (3.5 and above); Heavy weight. Example: Galena, Barite

Physical properties depending upon taste, odour and feel: Taste: The characters of minerals depend upon taste are only perceptible, when the minerals are soluble in water. The following terms are used related tastes. Saline taste – taste of common salt, Example: Halite

Alkaline taste – taste of potash and soda,

Bitter taste – taste of Epsom salt, Example: 4

Cooling taste – taste of nitre or potassium chlorate, Page

Sweetish astringent taste – taste of alum, Sour taste – taste of sulphuric acid.

Odour: Some minerals have characteristic odours when struck, rubbed, breathed upon or heated. Alliaceous or Arsenical: – Odour of garlic, given when arsenic compounds are heated. Example: . Sulphurous: – Odour of burning sulphur, given off by pyrites when struck, or by many sulphides when heated. Argillaceous: – the odour of clay when breathed upon. Example: Kaolin. Horse-radish odour: – Odour of decaying horse-radish, given when selenium compounds are heated. Foetid: – Odour of rotten eggs, given by heating or rubbing certain varieties of quartz or limestone.

Feel: soapy, smooth, greasy, harsh or rough, are kinds of feel of minerals that may aid in their identification. Examples: Soapy feel – steatite, greasy feel – gypsum, smooth feel – agate, harsh feel – native copper. Physical properties depending upon magnetism, electricity and radioactivity: Magnetism: Only few minerals are attracted by a bar magnet or horseshoe magnet. Of these, the most common are magnetite and . Some specimens of magnetite are themselves behaves like natural magnets are called lodestone.

Electricity: Most of the minerals with metallic lustre such as native metals and sulphides have a capacity for conducting electricity. Certain minerals develop an electric charge when subjected to a temperature change are called pyroelectric minerals. Example: . Certain minerals develop an electric charge when subjected to stress are called piezoelectric minerals. Example: Quartz.

Radioactivity: Many minerals containing elements of high atomic weight such as radium, uranium and thorium are radioactive and emit radiations. Example: , . Radioactive minerals are detected in the field by using Geiger counter and the scintillometer.

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