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DEFINITIONS
Beneficiation
Treatment of a crude ore in order to
improve it’s quality.
Example: beneficiating raw coal to a
steam coal for power generation or to
a coking coal for furnaces.
Liberation
Freeing of valuable minerals/metals
in an ore or mineral by
crushing and grinding.
Well Liberated Minerals
Poorly Liberated Minerals
Run-of-Mine Ore
Uncrushed ore in its natural
state just as it is when blasted.
Ore, as accepted for treatment
from the Mine.
Gangue
Waste rock that surrounds an ore deposit.
The waste material in an ore.
The valueless tailings/waste fraction of an ore rejected by a separating process.
Recovery
Indicates the proportion of
valuable material acquired
from the processing of an ore.
Generally stated as a percentage
of the values recovered compared
to the total values present.
Tailings
The neutralized waste discarded after
the economically recoverable metals
have been extracted from the ore.
Units
• 1 tonne/ton = 1000kg = 2204.6 lb• 1short ton = 2000 lb = 0.90718 tonne• 1 tonne = 32151 Troy ounces• 1 Troy ounce = 31.1035 gram• 1 oz/short ton = 34.2859 gram/tonne• 1 gram/short ton = 0.03215 oz/short ton• M or m = million, bn or billion = 1000 m
• All tons in this presentation are metric
ORESand
MINERALS
Rocks and MineralsRocks are aggregates of minerals.
Minerals are either elemental compounds (e.g. feldspars, pyroxenes, amphiboles and micas are rock-forming silicate minerals…) or free, uncombined native elements (e.g. gold, silver, copper…).
With a few exceptions (e.g. water, mercury, opal…) minerals are solid inorganic elements or elemental compounds with definite atomic structures and chemical compositions (within fixed limits).
The various types of coals are rocks.
Igneous rockIgneous rockfrom molten magma (intrusive)
or lava (surface),crystalline structure,
random or aligned crystals,no fossils
Metamorphic rockMetamorphic rockigneous, metamorphic or sedimentary rock changed by heat and pressure,
rare fossils, usually crystalline,
two types: foliated, wavy or more random structure,
e.g. gneisses
Sedimentary rockSedimentary rockform in layers or strata,
loosely grained, quartz often dominant,calcite in limestones,
contain fossils
Igneous Rocks Igneous Rocks (note: large masses of molten magma are called plutons)(note: large masses of molten magma are called plutons)
granite, pegmatite, granodiorite, syenite,anorthosite, agglomerate,gabbro, pyroxenite, kimberlite, peridotite
gabbro
quartz porphyry,microgranite,lamprophyre,dolerite, norite
dolerite basalt
rhyolite, andesite,pumice, tuff, obsidian, basalt,pitchstone, volcanic bomb,ropy lava
Metamorphic RocksMetamorphic Rocks
Foliated: gneisses, amphibolite, eclogite
Unfoliated: marbles, granulite, skarn
Foliated: schists, phyllite
Unfoliated: hornfels, marbles
Foliated: slates, phyllite
Unfoliated: marbles, skarn, mylonite
gneiss
schist slate
Sedimentary RocksSedimentary Rocks
mainly rock: conglomerate, breccia
mainly calcium carbonate: limestones
mainly rock: greywackemainly quartz: sandstones, arkosemainly calcium carbonate: limestones, travertine, tufaothers: potash, rock salt, dolomite, ironstone
mainly quartz: loess, shale, clay, mudstone mainly calc carbonate: chalk, marl, limestonesothers: peat, anthracite, lignite, amber, jet, chert, flint
quartz conglomerate
sandstone shale
GEOLOGICAL AND HUMAN TIME SEQUENCE OF THE EARTH
ERAS / AGES DIVISIONS (15 PERIODS/SYSTEMS) MILLIONS OF YEARS FOSSIL TYPESBEFORE PRESENT TIME OTHER IDENTIFICATIONS
IRON AGE 1200 - 500 BC iron artefacts
BRONZE AGE 3000 - 2000 BC bronze artefacts, first cities
Present Neolithic 9000 - 4000 BC Modern Man agriculture, towns Homo Sapiens
Mesolithic 10 000 BC bow & arrow
STONE AGE Upper Palaeolithic 30 000 BC stone & bone tools, artQUATERNARY
Palaeolithic Middle Palaeolithic 100 000 yrs Neanderthal Man specialised tools
Lower Palaeolithic 1.0 million Homo Erectus fire, tools
Pleistocene (nearly present) 1.6 includes ice-formed depositsat least 15 ice ages/retreats
PlioceneNeogene
Miocene (less than present) 26TERTIARY
Oligocene
Palaeogene Eocene (dawn of the present)
Paleocene 65
Cretaceous 140 chalk, limestone, dinosaurs"Age of Reptiles"
MESOZOIC Jurassic 210 dinosaurs"middle life"continental drift begins
Triassic 245
Permian 290
Carboniferous 365 coal age"Age of Amphibians"
Devonian 410PALAEOZOIC "Age of fishes""old life"
Silurian 440
Ordovician 500
Cambrian 570 trilobites
Proterozoic 2400 fossils now knownPRE-CAMBRIAN
Archaean 4500 no fossils
* Periods are divided into Upper Periods can be divided intoand Lower and sometimes, Middle Zones according to dominant
fossils, and may span 500 m yrseach or much less
VALUES HOST DEPOSIT EXAMPLE CHARACTERISTICS
Au
shear-hosted
paleo- conglomerates
Finniston, Sunrise Dam WA, Ashanti Ghana, Witwatersrand
Alluvial (Magaden Russia)
archaean mesothermal lode deposits in shear zones.
gold-bearing conglomerates from weathering of archaean greenstone belts. 7g/t.
Cu carbonatite Palabora proterozoic to recent intrusive magmatic carbonates and associated alkaline igneous rocks
Ag epithermalex hydrothermal fluids of extrusive /shallow intrusive igneous rocks.
Pb, Zn, Ag carbonate - hosted
Galmoy Ireland,Reocin Spain,Pine Point Canada
phanerozoic deposits in thick sequences of dolomite/limestone rocks. Formed in warm sea. 3-10%
Cu, Mo porphyry Escondida Chile low grade (0.5-2%) large deposits (1000 Mt). Molybdenum may occur.
Cu, Au
skarn
porphyry
Nickel Plate Canada,La Luz Nicaragua
Grasberg Indonesia,Bingham USA
phanerozoic deposits formed at high temps by igneous intrusions at convergent plate margins.
see Cu, Mo porphyrys
Cu, Zn volcanogene Neves Corvo Portugal, Black Mountain RSA
stratiform massive sulphide deposits between volcanic units
ORE DEPOSIT TYPES
VALUES HOST DEPOSIT EXAMPLE CHARACTERISTICS
Cu, Zn, Sn granite-hosted tin South Crofty UK deposits in granitic plutons. similar
to porphyry coppers. low grade.
Au, Cu, Ag sediment-hosted Muruntau Uzbekistan metals concentrate in hydrothermal fluids.
Cu, Ag kupferschiefer Lublin Poland stratiform sulphide deposits; marine or deltaic environments. proterozoic-tertiary sediments.
Au, Ag epithermal goldCarlin USA, McLaughlin USA, Lepanto Philippines
shallow deposits at convergent plates. vein and disseminated sulphide types.
Cu, Ni mafic sulphide- hosted
Mt Keith WA, Voisey Bay Canada
primary sulphides in igneous rocks in archaean greenstones. up to high tonnages.
Diamondskimberlite
alluvial & marine
Premier RSA
Kleinsee RSA
ultramafic rocks in volcanic pipes, sills. proterozoic and later.
weathering of kimberlites formed gem quality placer deposits.
Pt, Pd, Rh, Ir, Ru, Os
layered mafic intrusions Bushveld UG2 RSA
orthomagmatic sulphides in large layered igneous complexes. high temp magma formation & crystallization. proterozoic.
Pt, Pd, Rh, Ir, Ru, Os, Cu, Ni
layered mafic intrusions
Bushveld Merensky Reef RSA, Stillwater
as above. differences in geochemical evolution of magma concentrated Ni and Cu in layers.
ORE DEPOSIT TYPES (continued)
VALUES HOST DEPOSIT EXAMPLE CHARACTERISTICS
Pt, Pd, Rh, Au alluvial Goodnews Bay USA
sediment-hosted placer deposits from weathering of mafic igneous complexes, concentration of PGEs and Au by fluvial processes.
Pt, Pd, Rh, Ir, Ru, Au, Cu, Ni
layered mafic intrusions
Merensky Reef, Norilsk, Sudbury
same geological setting and genesis as before with Ni, Cu and Au concentrated in certain layers.
Coal open pit Witbank RSA,Griffin WA
shallow stratiform seams. overburden usually mid-to-late phanerozoic sediments.
Chromium chromitite Dwarsrivier RSA
chromitite in two deposit types. stratiform: ultrabasic layered igneous complexes. podiform: different structural form, tectonised ultrabasic sequences of ophiolote complexes.
Tantalum tantalite Greenbushes WAin sheared archaean granite-greenstone terranes. low volume, high value.
Other Minerals
laterite nickel
bauxite (Al)
stratabound iron
stratabound manganese
Murrin Murrin WA
Huntly WA
Thabazimbi RSA,Hammersley WA
Sishen RSA
extensive surface deposits. secondary mineralisation after weathering of crystalline parent rocks. high volume, low value.
ORE DEPOSIT TYPES (continued)
Placer Deposit
An alluvial deposit of ore, usually
a mineral-bearing gravel or sand.
Any concentration of the heavier
and more durable minerals that
have deposited from the actions
of erosional forces.
Kimberlites and Diamonds
KIMBERLITE
Crumbly, grey-green, often soft, igneous, ultrabasic, coarse grained
dark rock often with porphyritic texture and brecciated appearance. In peridotite rock mantle pocketed
with eclogite (50% garnet).
Usually found in archaean cratons of basement rock 2.5 billion years old. Youngest known diamond-bearing
pipe is 45 miilion years old.
Usually in pipes (hypabyssal occurrence in plutons) of up to 1km
diameter (largest 361 acres).
Primary mineral is serpentized olivine and associated minerals are
phlogopite, pyroxenes, carbonate, chromite, pyrope garnet, rutile and
perovskite.
DIAMOND
(Greek for indomitable – adamas)
Origin - kimberlite pipes
Gem - octahedra, cubes, dodecahedra, tetrahedra crystals.
Boart – rounded with radiating structure.
Carbonado – microcrystalline mass.
SG 3.52, hardness 10, carbon
INDICATOR MINERALS FOR DIAMOND-BEARING KIMBERLITES
Indicator minerals diamonds in kimberlites are chrome diopsides
(green), garnets (pink, purple, orange, yellow, green),
microdiamonds.
Pyrope garnets (shown):
some purple (or deep red) garnets have same high chrome low silica
chemical profile as diamonds (Harzburgitic signature). If these G10 garnets are not present there will be
no diamonds.
Eclogite rock can be very diamond-rich and contains orange garnets,
not G10s.
Kimberlite pipes often occur in clusters and different ilmenites in the pipes
assist in defining them.
LamproiteA second primary source of diamonds of potassium-rich hypabyssal lamprophyric rocks formed from magmatic intrusions (Miocene).Olivine lamproite and leucite lamproite are known to be diamond-bearing. Indicators minerals are chromites, andradite and zircon – garnets are rare.The AK1 deposit at Argyle Diamond Mine is a well-known lamproite orebody.The surface weathered ore has a Bond Work index of 10 kWh/t and an Abrasion Index of 0.22. The deeper more competent unweathered ore has a BWI of 18 and an AI of 0.60.
Hypabyssal
Intrusive igneous rocks
In smaller host bodies at intermediate depths, examples: dykes and sills
Medium to fine-grained
“Plutonic” if formed in very large masses at greatest depths, coarse-grained, visible minerals, e.g. batholiths
Carbonatites
Calcium carbonate (calcite)-rich rock
Magmatic !
Can contain magnetite, apatite, micas, sulphide minerals.
Basalts
Formed from “basic” lavasMost common of all volcanic rocksDark compact rocks (mafic), very fine-grained
Acid lavas form light low density rocks (felsic)
Of peculiar composition, found in moist-tropical regions. Crusty, reddish-brown deposits, hardened by precipitation of iron.
Laterite can develop through deep weathering and are rich in hydroxides of aluminium and iron, concentrated by the upward leaching by ground water due to the rapid surface evaporation of moisture.
Murrin Murrin in a laterite-hosted orebody typically 20 m in depth and 10 m overburden and has a nickel-cobalt mineralisation.
Bauxite, Al2O3.2H2O is a lateritic mineral.
Laterites
MINERALS
Mineral
Solid substance having a regular
and definite chemical composition
Mineral Content
Industrial minerals can have a high concentration of values such as 94% iron oxide in iron ore.
Base metals contents are often in the low percentages, e.g. copper 3%.
Precious metals ores usually have a tiny content of values, e.g. gold and platinum contents are typically 0.0005% or 5 gram/ton or 5 parts / million.
RESOURCES
RESOURCES AND RESERVES
IN SITU RESOURCESIN SITU RESOURCESreported as
mineralization in place
INFERREDINFERRED
INDICATEDINDICATED
MEASUREDMEASURED
EXTRACTABLE RESERVESEXTRACTABLE RESERVES reported as mineable production estimates
PROBABLEPROBABLE
PROVENPROVEN
consideration of mining, metallurgical, economic, marketing, legal, environmental, social and governmental factors
the modifying factorsthe modifying factors
increasing increasing level of level of
geological geological knowledge knowledge
and and confidenceconfidence
Reserves
That part of a mineral deposit which can
be economically and legally extracted at
the time of the reserve determination.
There are two categories of reserves:
Probable and Proven
Probable Ore
Tonnage & grade are computed partly from specific measurements (samples/production data) and partly from projections (geological evidence over a reasonable distance).
Refers to sites available for inspection, measurement and sampling but which are inappropriately spaced for outlining the ore completely or fully establishing it’s grade.
Proven Ore
Tonnage is computed from dimensions revealed in outcrops, trenches, drill holes, underground workings and grade from the results of adequate sampling.
The sites for inspection, sampling and measurement are so well spaced and the geological character so well defined that size, shape and mineral content are accurately established.