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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.
Well
Liberated
Minerals
Liberation
Poorly Liberated
Minerals
Freeing of valuable minerals/metals
in an ore or mineral by
crushing and grinding.
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
•
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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
ORES
and
MINERALS
Rocks and Minerals
Rocks 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 rock
from molten magma (intrusive)
or lava (surface),
crystalline structure,
random or aligned crystals,
no fossils
Metamorphic rock
igneous, 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 rock
form in layers or strata,
loosely grained,
quartz often dominant,
calcite in limestones,
contain fossils
Igneous Rocks
(note: large masses of molten magma are called plutons)
gabbro
dolerite
granite, pegmatite,
granodiorite, syenite,
anorthosite, agglomerate,
gabbro, pyroxenite,
kimberlite, peridotite
quartz porphyry,
microgranite,
lamprophyre,
dolerite, norite
basalt
rhyolite, andesite,
pumice, tuff,
obsidian, basalt,
pitchstone,
volcanic bomb,
ropy lava
Metamorphic Rocks
schist
slate
gneiss
Foliated: gneisses,
amphibolite, eclogite
Unfoliated: marbles,
granulite, skarn
Foliated: schists, phyllite
Unfoliated: hornfels,
marbles
Foliated: slates,
phyllite
Unfoliated: marbles,
skarn, mylonite
Sedimentary Rocks
quartz conglomerate
sandstone
mainly rock: greywacke
mainly quartz: sandstones,
arkose
mainly calcium mainly calcium carbonate:
carbonate:
limestones, travertine, tufa
limestones
others: potash, rock salt,
dolomite, ironstone
mainly rock:
conglomerate,
breccia
shale
mainly quartz: loess,
shale, clay, mudstone
mainly calc carbonate:
chalk, marl, limestones
others: peat, anthracite,
lignite, amber, jet, chert,
flint
GEOLOGICAL
ERAS / AGES
AND HUMAN TIME SEQUENCE
OF THE EARTH
DIVISIONS (15 PERIODS/SYSTEMS)
MILLIONS OF YEARS
BEFORE PRESENT TIME
IRON AGE
BRONZE AGE
Present
1200 - 500 BC
iron artefacts
3000 - 2000 BC
bronze artefacts, first cities
Neolithic
9000 - 4000 BC
Mesolithic
10 000 BC
STONE AGE
Upper Palaeolithic
FOSSIL TYPES
OTHER IDENTIFICATIONS
Modern Man
agriculture, towns
Homo Sapiens
bow & arrow
30 000 BC
stone & bone tools, art
QUATERNARY
Palaeolithic
Middle Palaeolithic
Lower Palaeolithic
Pleistocene (nearly present)
100 000 yrs
Neanderthal Man
1.0 million
Homo Erectus
1.6
specialised tools
fire, tools
includes ice-formed deposits
at least 15 ice ages/retreats
Pliocene
Neogene
Miocene (less than present)
26
TERTIARY
Oligocene
Palaeogene
Eocene (dawn of the present)
Paleocene
Cretaceous
65
140
chalk, limestone, dinosaurs
Jurassic
210
dinosaurs
Triassic
245
Permian
290
Carboniferous
"Age of Amphibians"
365
Devonian
"Age of fishes"
410
Silurian
440
Ordovician
500
Cambrian
570
"Age of Reptiles"
MESOZOIC
"middle life"
continental drift begins
PALAEOZOIC
"old life"
coal age
trilobites
Proterozoic
2400
fossils now known
Archaean
4500
no fossils
PRE-CAMBRIAN
* Periods are divided into Upper
and Lower and sometimes, Middle
Periods can be divided into
Zones according to dominant
fossils, and may span 500 m yrs
each or much less
ORE DEPOSIT TYPES
VALUES
HOST DEPOSIT
shear-hosted
Au
EXAMPLE
Finniston,
Sunrise Dam WA,
Ashanti Ghana,
Witwatersrand
CHARACTERISTICS
archaean mesothermal lode
deposits in shear zones.
gold-bearing conglomerates from
weathering of archaean greenstone
belts. 7g/t.
paleoconglomerates
Alluvial (Magaden
Russia)
Cu
carbonatite
Palabora
Ag
epithermal
ex hydrothermal fluids of extrusive
/shallow intrusive igneous rocks.
Pb, Zn, Ag
Galmoy Ireland,
carbonate Spain,
hosted Reocin
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.
skarn
Nickel Plate Canada,
La Luz Nicaragua
phanerozoic deposits formed at
high temps by igneous intrusions
at convergent plate margins.
porphyry
Grasberg Indonesia,
Bingham USA
see Cu, Mo porphyrys
volcanogene
Neves Corvo Portugal,
Black Mountain RSA
stratiform massive sulphide
deposits between volcanic units
Cu, Au
Cu, Zn
proterozoic to recent intrusive
magmatic carbonates and
associated alkaline igneous rocks
ORE DEPOSIT TYPES
VALUES
HOST DEPOSIT
EXAMPLE
(continued)
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
Au, Ag
epithermal gold
Carlin USA,
McLaughlin USA,
Lepanto Philippines
Cu, Ni
mafic sulphidehosted
Mt Keith WA,
Voisey Bay Canada
kimberlite
Premier RSA
alluvial & marine
Kleinsee RSA
Pt, Pd, Rh,
Ir, Ru, Os
layered mafic
intrusions
Bushveld UG2 RSA
Pt, Pd, Rh,
Ir, Ru, Os,
Cu, Ni
layered mafic
intrusions
Bushveld Merensky
Reef RSA, Stillwater
Diamonds
stratiform sulphide deposits; marine
or deltaic environments.
proterozoic-tertiary sediments.
shallow deposits at convergent
plates. vein and disseminated
sulphide types.
primary sulphides in igneous rocks
in archaean greenstones. up to high
tonnages.
ultramafic rocks in volcanic pipes,
sills. proterozoic and later.
weathering of kimberlites formed
gem quality placer deposits.
orthomagmatic sulphides in large
layered igneous complexes. high
temp magma formation &
crystallization. proterozoic.
as above. differences in
geochemical evolution of magma
concentrated Ni and Cu in layers.
ORE DEPOSIT TYPES
VALUES
HOST DEPOSIT
EXAMPLE
Pt, Pd, Rh,
Au
alluvial
Goodnews Bay USA
Pt, Pd, Rh,
Ir, Ru, Au,
Cu, Ni
layered mafic
intrusions
Merensky Reef,
Norilsk, Sudbury
Coal
open pit
Witbank RSA,
Griffin WA
Chromium
chromitite
Dwarsrivier RSA
Tantalum
tantalite
Greenbushes WA
laterite nickel
Murrin Murrin WA
bauxite (Al)
Huntly WA
stratabound iron
Thabazimbi RSA,
Hammersley WA
Other
Minerals
stratabound
manganese
Sishen RSA
(continued)
CHARACTERISTICS
sediment-hosted placer deposits
from weathering of mafic igneous
complexes, concentration of PGEs
and Au by fluvial processes.
same geological setting and genesis
as before with Ni, Cu and Au
concentrated in certain layers.
shallow stratiform seams.
overburden usually mid-to-late
phanerozoic sediments.
chromitite in two deposit types.
stratiform: ultrabasic layered
igneous complexes. podiform:
different structural form, tectonised
ultrabasic sequences of ophiolote
complexes.
in sheared archaean granitegreenstone terranes. low volume,
high value.
extensive surface deposits.
secondary mineralisation after
weathering of crystalline parent
rocks. high volume, low value.
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 diamondrich and contains orange garnets,
not G10s.
Kimberlite pipes often occur in clusters
and different ilmenites in the pipes
assist in defining them.
Lamproite
A 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” lavas
Most common of all volcanic rocks
Dark compact rocks (mafic), very finegrained
Acid lavas form light low density rocks
(felsic)
Laterites
Of peculiar composition, found in moisttropical 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.
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 RESOURCES
reported as
mineralization in place
EXTRACTABLE RESERVES
reported as mineable
production estimates
INFERRED
increasing
level of
geological
knowledge
and
confidence
INDICATED
PROBABLE
MEASURED
PROVEN
consideration of mining, metallurgical, economic,
marketing, legal, environmental, social and governmental factors
the modifying factors
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.