Transcript Chapter 30-35

Applied mineralogy
Chapter 30 to 35
Introduction to applied
mineralogy
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Practical application of mineralogical knowledge
Mineralogy – major economic significance
Gemology (Ch 31), mineral prospecting, mineral
extraction, chemical plants, cement industry (Ch 32),
medicine & environmental mineralogy (Ch 33)
 Growing field with developing needs – new
branches of applied mineralogy develop
 Indispensable in geology and petrology
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Chapter 30
Metalliferous mineral deposits
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Prospecting mineralogy
Economically important minerals
Geological setting of metal deposits
Convergent margins
 Divergent margins
 Precambrian shields
 Sedimentary basins
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Chapter 30
Prospecting mineralogy
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Occurrence and identification of mineral deposits, determine
mineralogical composition to classify and determine extractability
Traditionally rely on visual identification in field and sample
collection for laboratory investigations
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Mineralogical features primary criteria for prospecting
Currently more sophisticated analytical techniques
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Mineralogy knowledge integrated with geochemistry, petrology and
structural geology
Mineralogical prospecting partly replaced by remote sensing techniques
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Use electromagnetic spectrum reflected from different type of minerals on earth surface
Spatial distribution of mineral types identified on large scale
Especially useful in iron and gold deposits
Chapter 30
Economically important minerals
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Table 30.1 and 30.2
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Metalliferous minerals (Chapter 30)
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Fe, Mn, Ni, Cr, Si, Mo, Co, W
Cu, Zn, Pb, Sn, Hg
Al, Mg, Ti, Be
Au, Pt, Ir, Ag
Gemstones (Chapter 31)
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Ferrous metals:
Nonferrous base metals:
Nonferrous light metals:
Precious metals:
Diamond
Colour gems:
Corundum, beryl, tourmaline, topaz
Cement minerals (Chapter 32)
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Calcite, clay, gypsum
Chapter 30
Metal deposits
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Many metal deposits are related to RECENT
plate tectonic activity
Convergent margins
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Melting of subducting sediments along continental
shelf produce volcanism and batholithic intrusions
Igneous activity drives hydrothermal processes
Co and Mo, Hg
Divergent margins
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Largest magma extrusions
Seawater penetrates seafloor, heat up, react with
basalt and becomes acidic
Acidic water dissolves Cu, Pb, Zn, Co, Mn as trace
elements from basalt, transport metals and
concentrate them when precipitated as sulfides
and oxides when in contact with cold seawater
(VMS deposits)
Chapter 30
Metal deposits (cont)
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Precambrian shields
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Primary deposits of Cr, Ni, Pt much older
Orthogneisses and mafic to ultramafic volcanics
(greenstone belts) occur on these shields
Komatiites: ultramafic, very high T magma from
great depths
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Gold veins at contact with komatiites and
surrounding granite – Witwatersrand (placer
derived from above)
Layered chromite – Bushveld Complex: Cr, Pt,
Cr-magnetitie, V
Sedimentary basins
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BIFs: Algoma-type and Superior-type
Algoma: submarine hot springs release Fe-rich
hydrothermal solutions in sedimentary basins
alternated with Si-rich layers
Superior-type: no volcanism, associated with
limestones, formed at shallow-water coastal
environments, Fe and Si layers alternatively
brought from deep ocean to coast by upwelling
currents
Chapter 30
Metal deposits
Chapter 31
Gemstones
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Introduction
Instruments used by gemologists
Important gems
Gemstone enhancements
Crystal synthesis
Chapter 31
Introduction
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Def: minerals highly valued for beauty,
durability and rarity
Most precious gems exceed value of
same mass of gold by 3000 times
Many gems artificially produced for a
fraction of the price
Gems mostly permanent, BUT: some
coloured gems could lose colour due to
sunlight or heat exposure.
Small worldwide production in kg, but
yearly value equals that of cement
production.
Chapter 31
Gemology instruments
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Similar to mineralogical instruments – but has to be
non-destructive.
Energy dispersive X-ray fluorescence on gem surfaces
NB – binocular gemological microscope
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Dark / light field illumination to check inclusions, growth
features, treatment and synthesis
Gem refractometer, spectroscope, polariscope
Chapter 31
Important Gems
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Diamonds – upper mantle, kimberlites
Emerald – hydrothermal systems
Ruby, sapphire – high T environments: alkaline magmas and
aluminous metamorphic rocks
Aquamarine, topaz, tourmaline - pegmatites
Chapter 31
Gemstone enhancements
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Improve appearance by:
Cutting
 Heating to improve colour – often produce damage
and often non-permanent
 Filling cracks – can wear off, not as durable
 Dying – not stable, do not penetrate entire crystal
 Radiation to induce colour – also not always
permanent
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Chapter 31
Crystal synthesis
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Large market for synthetic gems, also for
industrial use
Different methods
Powder flame fusion: ruby and sapphire
 Czochralski melt growth: rubies for lasers, silicon
crystals, garnets
 Flux growth: emeralds
 Hydrothermal growth: quartz
 Ultra-high pressure: diamond
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Chapter 32
Cement minerals
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Significance of cement
Some features of nonhydraulic cements
Portland cement
Some problems with concrete
Chapter 32
Significance of cement
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Concrete is most widely used structural material in
world today.
1 billion tonnes of Portland cement converted into 11.5
billion tonnes of concrete
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Much weaker than steel, but preferred
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5 x more than steel consumption
Resistance to water
Formed into many shapes and sizes
Cheapest and most readily available building material
Concrete: cement + aggregate ( sand, gravel and/or
crushed rock)
Chapter 32
Types of cement
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Non-hydraulic cements
Harden by calcination; not resistant to water
 Minerals: Gypsym from anhydrite; calcite from lime
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Hydraulic cements
Harden by reacting with water; water resistant
 Portland cement: Ca-silicates and Ca-carbonates,
with Al- and Fe-oxides
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Chapter 32
Concrete problems
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Sulfate attack
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Alkali-silica reaction
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Sulfate in soil, seawater, acid rain
Cracking, permeability increase, loss of strength
Mainly when gypsum form when sulfate react with cement minerals and
has a volume increase
Siliceous minerals: opal, microcrystalline quartz, deformed quartz are
open for this reaction with alkali ions in pore system of cement: destroys
cement, increase permeability, swellling
Corrosion
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Steel bars corroded when solution enters concrete; corrosion products
have high volume – cause cracking around steel
Chapter 33
Minerals and human health
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Mineral-like materials in human body
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Apatite and other phosphate minerals
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Calcite, aragonite and vaterite
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Constructive part of teeth
Abnormal growths in glands, tumors, kidneys and
lungs
Magnetite, hematite, goethite, lepidocrocite
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Mostly as important part of bones and teeth
Also occurs as abnormal growths as kidney, urinary,
and gall stones; tumors; in lungs, glands, heart and
arteries
Urinary bladders
Also oxalates, urates and other organic
compounds
Chapter 33
Minerals and human health
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Minerals in nutrition
Halite – common mineral consciously ingested by
humans
 Also barite – filling in chocolate
 Kaolinite – in ice creams – stabilize when melting
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Chapter 33
Minerals and human health
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Minerals in nutrition (continued)
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Inorganic compounds known in market as ‘minerals’
– important as nutritional additives along with
vitamins
Macrominerals: Ca, Cl, Mg, P, K, Na, S – needed in large
quantities
 Microminerals: Cr, Co, F, Fe, Mn, Mo, Zn – needed in
trace quantities
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Mostly derived from ‘real minerals’
Deficiency as well as too high concentration of
most of these can cause severe health effects
Chapter 33
Minerals and human health
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Minerals as health hazards
Many minerals has been documented to cause
pulmonary diseases:
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Riebeckite – mesothelioma
Grunerite, actinolite, antophyllite, tremolite and chrysotile –
asbestosis
Quartz – silicosis
Coal - emphysema (pneumoconiosis)
Chemical contamination by mining
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Atmosphere, water (ground and surface)
Chapter 34
Minerals in the solar system
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Current theory for universe: ‘Big Bang’ produce
elements:
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Firstly light elements: He and H
During cooling denser matter condense and collapse –
nuclear fusion: up to Fe and Ni
Stellar explosions – supernovae: heavier elements
Meteorites
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NB information on solar space mineralogy
Different types: chondrites, achondrites, iron and stony iron
meteorites
Many unique meteorite minerals, but also minerals common
to the earth
Chapter 35
Mineral composition of earth
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Crust
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Mantle
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Heterogenous: Sedimentary and igneous rocks; oceanic and
continental crust
Feldspars, pyroxenes, quartz, olivine, amphiboles, micas >
80% of crust
Uniform
Olivine, enstatite, Cr-diopside and augite, spinels,
amphiboles, Ti-phlogopite, garnet, plagioclase, apatite,
diamonds, chromite
Core
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Heavy elements