OMM - Finals Exam

Stereographic Projection

• a perspective projection of the sphere, through a specific point on the sphere (the pole or center of projection), onto a plane (the projection plane) perpendicular to the diameter through the point

• 2D representation of 3D space

• more convenient to draw lines in 2D space compared to drawing planes

• a method used in crystallography and structural geology to depict the angular relationships between crystal faces and geologic structures, respectively

Poles

• Lines that are normal (perpendicular to the plane or face)

Interfacial Angle

• Angle between the planes/faces of a crystal

Wulff Net

In order to make plotting of the stereographic projection easier, a device called a stereographic net/stereonet/____ is used.

Primitive Circle 

• circle that surrounds the stereonet

Great Circles 

• curved lines that connect the points labeled N and S on the stereonet. The E-W and N-S axes, as well as the Primitive Circle are also ____

• Angular relationships between points can only be measured here

Small Circles

• highly curved lines that curve upward and downward on the stereonet. 

WILLIAM ROENTGEN

• discovered and produced X-rays in 1895

• noticed that a fluorescent screen from a cathode ray tube emitted a flash of light each an electrical discharge was passed

X-RAYS

• used in radiography to give shadow images of objects

• produced when any electrically charged particle of sufficient kinetic energy is rapidly decelerated

• High voltage is applied between two electrodes (tens of thousands of volts)

• electron source → cathode → anode

Roentgen’s ghostly skeleton

• first radiographic image taken

1912

In what year was the exact nature of x-rays was established and the discovery of x-ray diffraction

MAX VON LAUE, PAUL KNIPPING, WALTER FRIEDRICH

• directed a beam of x-rays at a crystal of copper sulfate and recorded the scattered beams of a photographic plate

Radiography

• resolution is limited to sizes of the order of 10^-1cm

Diffraction

• can resolve details of internal structure of the order of 10^-8cm

• a scattering phenomenon

• ____ of electromagnetic radiation occurs due to certain phase relations between 2 or more waves

X-RAY DIFFRACTION

can provide information on:

• crystallite size, microstresses and microstrains (from an analysis of line broadening)

• macrostrains (from an analysis of line shifts)

• total thickness in multilayer films (from analysis of low-angle Bragg peaks)

X-RAY AS ELECTROMAGNETIC RADIATION

• form of electromagnetic radiation with wavelengths between gamma and ultraviolet rays

• high energy electromagnetic radiation having energies from ~200eV to 1 MeV

• those used in diffraction have wavelengths in the range 0.5-2.5 Angstroms (vs. order of 6000 Angstroms for visible light)

  • 1 Angstrom = 0.1nm = 1x10^-10m

CONSTRUCTIVE INTERFERENCE

• the electric field vectors have the same magnitude and direction at the same instant at any point x measured along the direction of the propagation of the wave

• produces diffracted beams

DESTRUCTIVE INTERFERENCE

• two waves are completely out of phase when the waves annul each other

• decrease in the resulting amplitude

DIFFRACTED BEAMS

• just beams composed of a large number of scattered rays mutually reinforcing one another

DIFFRACTED X-RAY BEAMS

• built up of rays scattered by all the atoms of the crystal which lie in the path of the incident beam

• takes place only at those particular angles which satisfy the BRAGG LAW

• intensity is extremely small compared to that of the incident beam

REFLECTION

• takes place on a thin surface only

• occurs at any angle of incidence

• by a good mirror is almost 100% efficient

BRAGG LAW

• states the essential condition to be met for diffraction to occur

• incident beam, the diffracted beam, and plane normal are always coplanar

• angle between the diffracted beam and transmitted beam is always 2θ (diffraction angle)

ORE MINERALS

best ore deposits are those containing large amounts of ____

METALS OF VALUE

best metal ore minerals are those that contain large amounts of ____

METALLIC ORE MINERALS

most ____ are native elements, sulfides, sulfosalts, oxides, or hydroxides

Magmatic Ore Deposits (Igneous), Hydrothermal Ore Deposits (Sedimentary/Metamorphic), Sedimentary Ore Deposits

3 TYPES OF ORE DEPOSTIS

Metallic and Semi-metallic Elements, Nonmetallic Elements, Gems, Construction and Manufacturing, Fertilizer and Chemicals, Energy Sources

6 groups of mineral commodities

Metallic and Semi-metallic Elements

Gold, Silver, Copper, Iron, Manganese, Aluminum are examples of what group of mineral commodities?

Nonmetallic Elements

Potassium, Sodium, Phosphorus, Sulfur are examples of what group of mineral commodities?

Gems

Diamond, Sapphire, Agate are examples of what group of mineral commodities?

Construction and Manufacturing

Sand, clay, building stone, diatomite, talc, mica, zeolites are examples of what group of mineral commodities?

Fertilizer and Chemicals

Limestone, phosphate, potash, salt, nitrate, fluorite are examples of what group of mineral commodities?

Energy sources

Coal, oil, gas, uranium are examples of what group of mineral commodities?

CELLPHONE

Display:

• Silica sand

• Cassiterite (primary source of tin)

• Bauxite (for LED)

• Sphalerite (source of indium)

Electronics and Circuitry:

• Chalcopyrite (source mineral of copper)

• Tetrahedrite (primary source of silver)

• Silicon (source mineral is quartz)

• Arsenopyrite (source of arsenic)

• Tantalite (source mineral of tantalum)

• Wolframite (source of tungsten)

Battery:

• Spodumene (source of lithium)

• Graphite

Speakers and Vibration:

• Bastnaesite (source of rare-earth elements to produce magnets)

 

Cassiterite

• primary source of tin

Bauxite

• source of LED

Sphalerite

• source of indium

Chalcopyrite

• source mineral of copper

Tetrahedrite

• primary source of silver

Silicon

• source mineral is quartz

Arsenopyrite

• source of arsenic

Tantalite

• source mineral of tantalum

Wolframite

• source of tungsten

Spodumene

• source of lithium

Bastnaesite

• source of rare-earth elements to produce magnets

MINERAL DEPOSIT

• a place in Earth’s crust where geologic processes have concentrated one or more minerals at greater abundance than in the average crust

ORE DEPOSITS

• a mineral deposit that can be produced to make a profit

• all ____ are mineral deposits, but not all mineral deposits are ____

EXAMPLES OF NATURAL ABUNDANCES OF ELEMENTS

Make up 99% of the Earth’s crust:

• Oxygen

• Silicon

• Aluminum

• Iron

• Calcium

• Sodium

• Potassium

• Magnesium

• Titanium

NATURAL ABUNDANCES OF ELEMENTS

• elements that occur in high abundance do not need a high concentration factor

• less common (chromium, lead, tin, and zinc) require great concentrations to be profitably mined

• there is a correlation between the economical ore grades and the price of a given resource

  • the more common the element, the cheaper it is

  • less common means higher price

  • if it is in-demand, the value of the mineral/ore increases

LESS ABUNDANT ELEMENTS

Radioactive elements:

• Uranium

• Thorium

Fertilizer:

• Nitrogen

• Phosphorus

US

• controls about half the world’s molybdenum

Australia

• produces about a quarter of the world’s aluminum

Zaire

• half of the world’s cobalt

South Africa

• controls 90% of the world’s platinum, half the world’s gold, and 75% of the chromium.

Bolivia and Brazil

• much of the world’s tin

China

• accounts for 95% of all rare earth production

Gold, Silver, Copper, Platinum

4 NATIVE METALS

Arsenic, Antimony, Bismuth

3 NATIVE SEMI-METALS

Graphite, Diamond, Sulfur

3 NATIVE NONMETALS

Silver

• sometimes occurs in a wire-like or arborescent (tree-like) form

Copper

• occurs in a variety of ore deposits associated with mafic volcanics and in some sandstones (branching sheets, plates, and wires, and as massive pieces )

Platinum

• from ultramafic igneous rocks or in placers; a secondary product of Cu- or Ni-sulfide refining

Antimony

• rarely pure and is usually in solution with arsenic and may contain small amounts of other metal

Sulfur deposits

• associated with volcanoes; concentrated at fumaroles

Graphite

• a minor mineral in many kinds of metamorphic rocks

Diamond

• only forms at very high pressures

OXIDES

• metals + oxygen

HYDROXIDES

• metals + OH

MAGMATIC ORE DEPOSITS (IGNEOUS)

• elements may not be concentrated enough to make mining economical

Disseminated deposit

• if the minerals are scattered throughout a host rock, but in sufficient amounts to mine profitably

Vein deposit

• consisting of veins that are centimeters to meters thick

Lode deposit

• ore is distributed in many small veins

Magmatic Sulfides and Cumulates

• Major elements: O, Si, Al, Fe, Ca, Na, K, and Mg

• Minor elements: S, Fe, Ni, Pt, Pd, etc.

Magmatic sulfide deposits

• pentlandite (Fe,Ni)9 S8, chalcopyrite (CuFeS2), pyrrhotite (Fe1-xS), and pyrite (FeS2)

Cumulate sulfide deposits

• account for almost 60% of the world’s nickel production and more than 95% of platinum and palladium production

Pegmatites

• name given to coarse-grained igneous rocks that form during the final stage of magma crystallization

• often mined for minerals rich in boron, cesium, lithium, molybdenum, niobium, tantalum, tin, tungsten,etc.

Kimberlites

• named after the town of Kimberly, South Africa, where they were first described, are volcanic rocks that originate in Earth’s mantle

• mined exclusively for diamonds 

HYDROTHERMAL ORE DEPOSITS (SEDIMENTARY/METAMORPHIC)

• as a melt (lava/magma) cools and crystallizes, hot, water-rich fluids may be released

• hydrothermal fluids dissolve other elements as they flow through rocks and eventually cool to deposit minerals in hydrothermal deposits

                

Porphyry Deposits

• special kind of hydrothermal deposit

• form when hydrothermal fluids carry metals toward the surface and deposit minerals to create disseminated ore deposits

Skarn Deposits

• are contact metamorphic zones that develop around an intrusion

• can form in any kind of rock, but most are associated with limestone or dolostone

• calcite and dolomite, and many Ca-, Mg-, and Ca-Mg-silicates

• are valuable mineral deposits containing copper, tungsten (75%), iron, tin, molybdenum, zinc, lead, and gold

Volcanogenic Massive Sulfides, Exhalitive Deposits

• when hydrothermal fluids create ore deposits at, or near, Earth’s surface, we call the deposits ____

Epigenetic Deposits

• when a hydrothermal deposit is not directly associated with a pluton, we call it an ____

• galena (PbS) and sphalerite (ZnS)

 

Placer Deposits

• heavy minerals, weathered from igneous, sedimentary, or metamorphic rocks, can be picked up and rivers may transport them long distances before they become concentrated in placers

• Spanish for alluvial sand

• copper or gold, sulfide minerals such as pyrite or pyrrhotite, and oxide minerals such as magnetite or ilmenite

Iron Ores

• banded iron formations (BIF) which are massive in scale

• if they contain especially significant amounts of magnetite and hematite, they are profitably mined

• contains repeating layers of black to silver iron oxide (magnetite), and red chert (microcrystalline quartz), magnetite (Fe3O4 ) and hematite (Fe2O3 ) but siderite (FeCO3 ), and the iron hydroxides goethite and limonite

Evaporites

• mined for many things, most notably halite, sylvite, and gypsum

• produce boronand lithium-mineral ores

Laterite Deposits

• water leaches rocks and soils, dissolving and carrying away soluble material

• the remains, called residuum, may be rich in aluminum, nickel, iron, or other insoluble elements

Phosphorites

• an essential nutrient

• have used it as a fertilizer

• most phosphorus comes from phosphorite