Mineral Dressing Intro

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What is a Mineral?A mineral:is a naturally occurring inorganic crystalline solidhas an ordered internal arrangement of atomshas specific physical properties that are either fixed or that vary within some defined range.has a definite chemical composition that may vary within specific limits2/24/20151

Ores:- Is natural aggregation of minerals from which metal or metallic compound can be recovered with profit on large scale The physical properties of minerals play the most important role in the economic processing of various ores2/24/20152PHYSICAL PROPERTIES OF MINERALS: The properties that can be determined with out the use of chemical tests. Depends on the kinds and arrangements of atoms in their crystal structures These can be used for quick identification of minerals they are:1) Transparency2) Luster3) Colour4) Luminescence5) Specific gravity

Quartz Amethyst

2/24/201536) Hardness7)Tenacity and Brittleness8) Cleavage9) Fracture10) Magnetic properties11) Electrical and Optical properties12) Radio active properties13) Physicochemical properties

2/24/20154Transparency:

The ease with which we can see through a mineral.Three classification: 1) Opaque 2) Transparent 3) TranslucentOpaque:Minerals through which no light can be seen.example: silver, copper, galena, pyrite etc. Transparent:Those minerals which can be seen through clearly.example: dolomite, calcite, diamond etc. 2/24/20155

Dolomite cluster- Transparent

Translucent rose Quartz52/24/20156Translucent: Those through which light can be seen. Light is diffused so that images cannot be seen clearly;example: impure quartz, calcite etc. Minerals are rarely pure hence different samples of the same mineral may show different degrees of transparency. 2/24/20157Luster: the amount and quality of the reflection of light from the mineral surface it refers to the surface appearance of the minerals like transparency it cannot be measured. minerals which look like metals are said to have metallic lusterminerals having non metallic luster.

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Pyrite: Metallic, Shiny Luster

Halite :Non-Metallic Translucent LusterCopyrightDr. Richard Busch

Sulfur :Non-Metallic Waxy LusterCopyrightStoneTrust, Inc. .

Minerals with a metallic luster are described as shiny, silvery, or having a metal-like reflectance. Non-metallic minerals may be described as resinous, translucent, pearly, waxy, greasy, silky, vitreous/glassy, dull, or earthy Luster may be subjective, and thus is not always a reliable identifier

2/24/20159 Luster depends on the way in which the atoms and their arrangement Both diamond and graphite are composed of carbon atoms, but graphite is metallic and diamond is adamantine. The difference in luster is due to the arrangements of atom in these two minerals

Adamantine- DiamondDull- KaoliniteGreasy- OpalMetallic- Pyrite2/24/201510

Pearly-MuscoviteResinous- AmberSilky- GypsumSub metallic- SphaleriteVitreous-QuartzWaxy - Jade2/24/201511Color: Color of the mineral is due to absorption of certain wavelength of light energy by the atoms making up the crystal. the remaining wavelength of the light that are not absorbed gives the sensation of color to the eye. few minerals have characteristic colours by which they can be recognized. combination of wavelength give rise to other intermediate colours. colours can be measured by determining the wavelength of light transmitted using spectrophotometer

2/24/201512 metallic minerals are generally of constant colour unless some surface alteration or tarnish has occurred

RUBY

EmeraldMolybdenite: -bluish-steely-grey

2/24/201513Some of colours of quartz:

2/24/201514LUMINESCENCE:

It refers to the emission of light by a mineral which is not the direct result of incandescence. It is faint in almost minerals and can be seen only in dark. Minerals which luminescence during exposure to ultra violet and x rays are called fluorescent. When the luminance continues after the rays are cut off the minerals is said to be phosphorescent. Fluorescence is produced when the energy of the short wave radiation is absorbed by the minerals/ions and released as longer wave radiation Fluorescence is unpredictable property Fluorite:- has blue fluorescence This property is used in identification and sorting of minerals2/24/201515Specific Gravity:It is constant for a mineral, may vary with presence of impurity The difference in specific gravities forms the basis of a class of ore dressing process known as gravity concentration methods.

2/24/201516Hardness: Ability to resist scratching This is different from the ease with which it can be broken. Diamond is the hardest material known 140 times harder than corundum., but it can be shattered eaisly. Hardness of a material is a characteristic property and can be measured.

Mohs Scale of Mineral Hardness2/24/201517 Hardness depends upon the forces holding the atoms of the mineral together. In 1812, a scientist, F. Moh devised a scale of hardness into which all minerals can be placed. He selected ten minerals and arranged them in order so that any one mineral could be used to scratch only minerals which are less. 2/24/201518Tenacity Brittleness and friability Refers to the breaking strength of minerals gold is a soft mineral but it requires a great force to break it. this include the resistance of a mineral to shock, crushing, cutting, and bending action The smaller the grains, the tougher the material- more force needed in comminuting.

2/24/201519Terms used to describe tenacity of minerals:-1. Malleable- These minerals are very soft and can be beaten to thin sheets without breaking( Native metals of Cu, Au, Ag).2. Brittle- These minerals are very hard but crumble to pieces under shock load - Diamond, quartz.3. Elastic- This type of minerals can be bent , but they spring back on removal of the bending force Muscovite-common mica KAl2(AlSi3O10)(F,OH)2 ,4. Flexible- They can be bent but remains distorted on removing the bending force- Gypsum CaSO42H2O, flakes of molybdate2/24/201520Cleavage:

Cleavage refers to the tendency of a mineral to break along planes of weakness in the chemical bonds, or along planes where bond strength is the least.

Courtesy United States Geological Surveyplane one:plane two: Feldspar: Two Cleavage Planes2/24/201521Some minerals break along one dominant plane of cleavage producing parallel sheets, where as others may break along two or more planes of cleavage, producing blocks or prism shapes. Not all minerals have distinct planes of weakness that produce cleavage, but those minerals that do, will consistently produce predictable cleavage planes.

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2/24/201523Fracture:Fracture refers to the non-planar breakage of minerals. it refers to appearance of surface minerals when broken

Conchoidal Fractures on a Quartz Mineral copyrightDr. Richard Busch2/24/201524Minerals that break along fractures (as oppose to cleavage planes) do not exhibit predictable weakness along specified bonds. Fractures may be described as splintery, uneven, or conchoidal Types: CONCHOIDAL FRACTURE- has concentric sets of cracks looks like the concentric ripples of a musselshell Eg:- glass, quartz, olivine etc.

2/24/201525EARTHY FRACTURE- looks like freshly broken soil. It is frequently seen in relatively soft, loosely bound minerals, such as limonite, kaolinite, aluminite ..

HACKLY FRACTURE(JAGGED FRACTURE) - jagged, sharp and not even. It occurs when metals are torn, and so is often en countered in native copper, and silver.2/24/201526Streak refers to the color of a minerals powdered form left behind after it is scraped or rubbed across a porcelain streak plate. A mineral may appear one color and then produce a streak with a different color.A minerals streak color is a more reliable identification characteristic than the minerals perceived surface color. Red chalk on a chalk board makes red marks. White chalk makes white marks.

STREAK2/24/201527Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.

Hematites color is grey, but its streak is red. Hema means blood. The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.

2/24/201528Magnetic Properties: it refers to the ways in which minerals react when placed in a magnetic field. Types:Diamagnetic: the minerals which are slightly repelled eg:- fluorite, calcite, quartz.2. Paramagnetic:the minerals which are weakly attractedeg:- Hematite, Biotite,Beryl.3. Ferromagnetic: the minerals which are strongly attracted by a magneteg:- magnetite, pyrrhotite. 2/24/2015294. Anti-ferromagneticthe interaction of adjacent atoms may be such as to align the spins in parallel but opposite directions called antiparallel spins. The two sets of magnetic moments cancel each other and there is no permanent magnetic moment5. Ferrimagneticthese are the cases of antiparallel alignment in which the components in opposed directions are not equal. Eg:-magnetite2/24/2015302/24/201531

Para magnetism Ferromagnetism Anti ferromagnetism FerrimagnetismEnforced ferromagnetism 2/24/201532Electrical Properties:Minerals are either conductors or non-conductors Some non conductors have the power to produce electricity when heated or put under pressure Gold, platinum copper etc. are conductors. Quartz, tourmaline calcite etc. are non-conductors. Tourmaline crystals when subjected to temperature change develops an electric current is called pyroelectricity Quartz crystals produce an electric current when the crystal is pressed called as piezoelectricity2/24/201533Radioactive Properties: The minerals that emit high- energy radiation are called radioactive the property depends on the presence of unstable atoms which are giving off radiation (-rays -rays -rays) to achieve a more stable state The presence of radiation can be detected and measured with devices like scintillation counter Uraninite, Thorite

2/24/201534Optical Properties: Refractive index Polarization Absorption 2/24/201535In diamond the 'fire' and sparkle is caused by dispersion as the gemstone acts like a prism

The brilliant colours displayed by opal are caused by the light being scattered as it passes through planes of regularly spaced voids between the transparent silica spheres.

2/24/201536Friction: The ability of particles to move or slide on a surface The automatic slate pickers used in cleaning coal take advantage of this principle 2/24/201537Mineral Aggregation:it is easier to recover valuable minerals from ores when they occur in pure and relatively large mass 2/24/201538Physicochemical properties: change of porosity of heat:

Certain minerals loose volatile constituents on heating.They become spongy.The pores get filled with air.This lowers apparent specific gravity

2/24/201539Decrepitation:Decrepitation is the act of heating up a mineral to the point that it crackles or fly to pieces until the crackling stops.

This is due to unequal expansion within the mineral molecules on heating.

Eg Calcite, Flourite, Barite.

This property is used to separate minerals that decripitate

2/24/201540change of magnetism by heat

Slightly magnetic / non magnetic Minerals of iron loose oxygen, carbonic acid, sulphur etc and become strongly magnetic .Certain minerals loose volatile constituents on heating.They can be separated out now with the aid of a magnet.

2/24/201541SURFACE PROPERTIES:Surface properties like greasiness, adhesion, wettability, surface tension etc are used for separating minerals ( flotation, amalgamation, selective adhesion etc)

Surface properties may be modified using chemical reagents.

SELECTIVE DISSOLUTION-

Dissolve either the valuables or the gangue selectively using chemicals.

Eg: in Gold Cyanidation , Au is dissolved in cyanide and removed from the impurities. It is later Recovered.