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IDENTIFICATION OF MINERALS SUPRABHA M.S
1st year PG scholar, Dept. of Rasa Shasta
S.J.G.A.M College, KOPPAL |
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THE EARTH Earth's interior has been sorted by Gravity. Heavier elements like iron tend to sink toward the center or core of the earth. Lighter materials, the silicates, oxygen compounds and water have risen to become part of the crust.
The Inner Earth is composed of three main parts; the crust, the mantle, and the core.
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The Crust - silicate rocks, primarily granite.
Oceanic Crust
Continental Crust - igneous, metamorphic, and sedimentary rocks
The Mantle - iron and magnesium rich silicate rocks
Upper Mantle
Lower mantle
The Core - iron nickel alloy
Outer core
Inner core |
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The Crust
Oceanic crust - The crust under the oceans and is generally made up of rock rich in iron and magnesium.
Continental crust - It is made up of igneous, metamorphic, and sedimentary rocks.
The Mantle
The upper mantle
Is made up of rocks rich in magnesium and iron, and poor in silica.
The Lower mantle
It is more dense and contains a greater amount of iron than the upper mantle
The core The core is composed primarily of a nickel-iron alloy. There is an outer core that is liquid and an inner core that is solid. |
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What are Rocks, minerals and crystals? Rocks consist of two or more minerals.
A mineral is any element or compound, normally occurring naturally as crystals.
A crystal is a structure. A mineral is a material.
A crystal is a regular arrangement of atoms, ions, or molecules in a solid. This regular internal structure leads to a geometrically regular external shape. Sodium chloride (common salt) crystals, for example, are cubic. |
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How to identify a mineral? Crystal structure
Crystal form – shape of crystal
Color
Luster – what the surface looks like in the light
Transparency -The ability to transmit light.
Tenacity – toughness
Cleavage – pattern when mineral is broken
Fracture
Hardness– what it can scratch & what scratches it
Specific gravity– how heavy it feels, heft.
Special Properties– magnetism , fluorescence, odor, streak, flame test, conductivity, Taste |
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1. Crystal Structure Crystal structure -A crystal structure is the orderly geometric spatial arrangement of atoms in the internal structure of a mineral.
Depending on the symmetry we can find Six types of crystal structure:
Isometric
Tetragonal
Orthorhombic
Monoclinic
Hexagonal
Triclinic |
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a. Isometric The isometric system are referred to three axes of equal lengths and at right angle to each other. ex: ironpyrite
b. Tetragonal
The tetragonal system are referred to Three axis at right angle to each other of which two horizontal axis are equal in length the vertical axis is either shorter or longer. ex:calcite
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c. Orthorhombic The orthorhombic system is referred to three axes at right angles to each other, all of different length. Ex :adamite d. Hexagonal The hexagonal system is reffered to to four axes, three equal horizontal axes in a common plane intersecting at 60 degree, and a fourth vartical axes at right angle to them. ex: beryl |
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e. monoclinic The monoclinic system are referred to three unequal axes, having one of their axial inclination oblique. Ex: gypsum
f. Triclinic
The Triclinic system are referred to three unequal axes, with all their intersections oblique. ex: labradorite
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g. Amorphous There's other type of crystals called amorphous in which crystals have no symmetry, this means that crystal system is absent, Amber and Opal are a good example. |
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2. CRYSTAL FORM (Habit) Crystal form indicates Shape of crystal .Based on shape crystal can be can classified as
Cubic - ex: pyrite
Rhombohedra - ex: dolomite
Tabular - ex: barite
Leafy - ex: Leafy barite
Columnar - ex: tourmaline |
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3. COLOR Color can be explained in two ways that is
Metallic
Non metallic
Examples for metallic
Peacock feather color – peacock ore
Copper color- copper
Black color - magnate
Examples for non metallic
Deep blue color – lapis lazuli
White color – gypsum
Yellow color - sulfur |
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4. LUSTER Luster indicates the way a mineral's surface interacts with light and can range from dull to glassy (vitreous).
Metallic – high reflectivity like metal: pyrite
Sub-metallic – slightly less than metallic reflectivity: magnetite
Non-metallic luster:
Adamantine – brilliant, the luster of diamond
Vitreous – the luster of a broken glass: quartz
Pearly – iridescent and pearl-like: pearl
Resinous – the luster of resin : sulfur
Silky – a soft light shown by fibrous materials: gypsum
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5. TRANSPARENCY Transparency - describes how well light passes through a mineral; there are three basic degrees of transparency: |
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6. TENACITY Tenacity is how tough a mineral is, how easily a mineral will break, split, crumble or change shape.
Elastic - can be bent & when let go they resume their previous shape. ex: mica
Ductile - can be pulled to make very thin threads .ex: gold
Fragile -break into pieces easily. ex: Sulpur
Friable - crumbles easily. ex: talc
Malleable -flatten out into thin sheets without breaking.
ex: gold
Sectile - can be cut with a blade .ex: gypsum |
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7. HARDNESS Hardness- the physical hardness of a mineral is usually measured according to the Mohs hardness scale. This scale is relative and goes from 1 to 10. A mineral with a given Mohs hardness can scratch the surface of any mineral that has a lower hardness than itself.
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The other tools for hardness test are :
Your thumb nail (hardness 1-2)
a copper coin (3)
The blade of knife (4-5)
A nail file (6)
Glass (6-7). Hardness test on Gypsum Hardness test: The glass is harder than the mineral (Talc) Test on glass – it is scratched (Citrine Quartz) |
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8. CLEAVAGE Cleavage is the tendency of minerals to split along certain defnite planes. Cleavage can be described as perfect, good, poor. Their are different types of cleavage they are
Basal cleavage occurs parallel to the base of a crystal. ex: Boitite
Cubic cleavage occurs on the planes, parallel to the faces of a cube for a crystal with cubic symmetry. ex: Glane
Octahedral cleavage occurs on the crystal planes, forming octahedral shapes for a crystal with cubic symmetry. ex: fluorite BASAL OCTAHEDRAL CUBIC |
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9. FRACTURE Fracture is when a mineral breaks, but the surface is not regular.
Conchoidal - curved break like what happens with thick glass, shell shaped. ex: quartz
Uneven - rough surface, not smooth. ex: metals
Even-the fracture surface is flat.
ex: kolin
Hackly-the broken edge shows sharp and jagged projections. ex: gypsum |
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10. SPECIFIC GRAVITY Specific Gravity (SG) indicates how many times more the mineral weighs compared to an equal amount of water (SG 1).
The specific gravity of minerals are known to vary from 0.8 to 21.
Borax is < 2 , where as platinum is > 20.
Instruments used for measuring the specific gravity are shown below
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11. STREAK Streak - refers to the color of the powder of a mineral leaves after rubbing it on an unglazed porcelain streak plate.
Note streak is not always the same color as the original mineral.
ex: hematite – red color streak. |
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12. FLUORESCENCE TEST Fluorescence-this is the property of substance, which emit light when it is subjected to irradiation with ultra-violet or other long wave rays.
It is a characteristic feature of some minerals. For ex :sulfur and calcite Calcite and Sulfur using a long wave length UV light source Calcite and Sulfur using a natural light source |
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13. ACID TEST, FLAME TEST ACID TEST (fizz test) : In this test you can test chemical properties for some minerals. For example, a few drops of hydrochloric acid (dilute or concentrated) can be used to see bubbles form the mineral. Ex: iron pyrite
FLAME TEST : In flam test when mineral subjected to flame, the color of flame will change. Ex: gold-yellow color flame. FIZZ TEST FLAME TEST |
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14. CONDUCTIVITY, MAGNETISM Conductivity – When a mineral subjected for conductivity process their will flow of current from positive end to negative end.
ex: copper
Magnetism- A few minerals in their natural state, are capable of being attracted by a magnet. Ex: hematite CONDUCTIVITY MAGNETISM |
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15. TASTE, ODOR TEST Taste test for minerals : all the minerals can’t be tasted only few of them can be tasted
Ex: Halite – Salt taste
Silvate – bitter taste
ODOR test : Some minerals have their characteristic odor.
Ex: Sepentine when dipped in water – mud odor
Gandaka when crushed has - bad odor |
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DISSUSION Most of the identification criteria are explained in Ayurveda some of them are as follows.
Color – qÉrÉÑUMühPû, lÉÏsÉÉ‹lÉÉãmÉqÉÇ.
Luster – lÉuÉÌlÉiÉmÉëpÉ, qÉWûÉå‹uÉsÉqÉ.
Specific Gravity – pÉUiÉÉåÅÍkÉMüqÉç , aÉÑÂ.
Cleavage – mÉ×jÉÑSsÉqÉ, ÌlÉqÉÉåïcrÉmɧÉÇ
Crystal form – A¹ÉxÉë, A¹ÉTüsÉMü, wÉOèûMüÉåhÉÉã.
Streak test - Suvarna maksika rubbed on MüwÉ golden line formed. |
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CONCULISION Identification of minerals plays a very important role while preparing the medicines. There are abundant minerals available which looks alike.
Minerals are expensive so the detailed tests are needed to chose the proper mineral.
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