Chapter 30 to 35

Applied mineralogy

Introduction to applied mineralogy

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

Chapter 30Metalliferous mineral

deposits Prospecting mineralogy Economically important minerals Geological setting of metal deposits

Convergent margins Divergent margins Precambrian shields Sedimentary basins

Chapter 30Prospecting mineralogy

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 Mineralogical features primary criteria for prospecting

Currently more sophisticated analytical techniques Mineralogy knowledge integrated with geochemistry,

petrology and structural geology Mineralogical prospecting partly replaced by remote

sensing techniques 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 30Economically important

minerals Table 30.1 and 30.2 Metalliferous minerals (Chapter 30)

Ferrous metals: Fe, Mn, Ni, Cr, Si, Mo, Co, W Nonferrous base metals: Cu, Zn, Pb, Sn, Hg Nonferrous light metals: Al, Mg, Ti, Be Precious metals: Au, Pt, Ir, Ag

Gemstones (Chapter 31) Diamond Colour gems: Corundum, beryl, tourmaline, topaz

Cement minerals (Chapter 32) Calcite, clay, gypsum

Chapter 30Metal deposits

Many metal deposits are related to RECENT plate tectonic activity

Convergent margins Melting of subducting sediments

along continental shelf produce volcanism and batholithic intrusions

Igneous activity drives hydrothermal processes

Co and Mo, Hg Divergent margins

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 30Metal deposits (cont)

Precambrian shields 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

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 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 30Metal deposits

Chapter 31Gemstones

Introduction Instruments used by gemologists Important gems Gemstone enhancements Crystal synthesis

Chapter 31Introduction

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 31Gemology instruments

Similar to mineralogical instruments – but has to be non-destructive.

Energy dispersive X-ray fluorescence on gem surfaces

NB – binocular gemological microscope Dark / light field illumination to check

inclusions, growth features, treatment and synthesis

Gem refractometer, spectroscope, polariscope

Chapter 31Important Gems

Diamonds – upper mantle, kimberlites Emerald – hydrothermal systems Ruby, sapphire – high T environments: alkaline

magmas and aluminous metamorphic rocks Aquamarine, topaz, tourmaline - pegmatites

Chapter 31Gemstone enhancements 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

Chapter 31Crystal synthesis

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

Chapter 32Cement minerals

Significance of cement Some features of nonhydraulic

cements Portland cement Some problems with concrete

Chapter 32Significance of cement

Concrete is most widely used structural material in world today.

1 billion tonnes of Portland cement converted into 11.5 billion tonnes of concrete 5 x more than steel consumption

Much weaker than steel, but preferred 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 32Types of cement

Non-hydraulic cements Harden by calcination; not resistant to

water Minerals: Gypsym from anhydrite;

calcite from lime Hydraulic cements

Harden by reacting with water; water resistant

Portland cement: Ca-silicates and Ca-carbonates, with Al- and Fe-oxides

Chapter 32Concrete problems

Sulfate attack 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 Alkali-silica reaction

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 Steel bars corroded when solution enters concrete;

corrosion products have high volume – cause cracking around steel

Chapter 33Minerals and human

health Mineral-like materials in human

body Apatite and other phosphate

minerals 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

Calcite, aragonite and vaterite Constructive part of teeth Abnormal growths in glands, tumors,

kidneys and lungs Magnetite, hematite, goethite,

lepidocrocite Urinary bladders

Also oxalates, urates and other organic compounds

Chapter 33Minerals and human

health Minerals in nutrition

Halite – common mineral consciously ingested by humans

Also barite – filling in chocolate Kaolinite – in ice creams – stabilize when

melting

Chapter 33Minerals and human

health Minerals in nutrition (continued)

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

Mostly derived from ‘real minerals’ Deficiency as well as too high

concentration of most of these can cause severe health effects

Chapter 33Minerals and human health Minerals as health hazards Many minerals has been documented to

cause pulmonary diseases: Riebeckite – mesothelioma Grunerite, actinolite, antophyllite, tremolite

and chrysotile – asbestosis Quartz – silicosis Coal - emphysema (pneumoconiosis)

Chemical contamination by mining Atmosphere, water (ground and surface)

Chapter 34Minerals in the solar

system Current theory for universe: ‘Big Bang’

produce elements: 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

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 35Mineral composition of

earth Crust

Heterogenous: Sedimentary and igneous rocks; oceanic and continental crust

Feldspars, pyroxenes, quartz, olivine, amphiboles, micas > 80% of crust

Mantle Uniform Olivine, enstatite, Cr-diopside and augite,

spinels, amphiboles, Ti-phlogopite, garnet, plagioclase, apatite, diamonds, chromite

Core Heavy elements