HOW ARE MINERAL
SANDS MINED ON NORTH
STRADBROKE ISLAND?
INSTRUCTIONS FOR VIEWING
THIS PRESENTATION
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Follow the links in grey to view more information on the
different steps involved in the mining of mineral sands.
THE SAND MINING PROCESS
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EXPLORATION DRILLING
FINDING
THE
MINERAL
The aim is to identify where the minerals are in economically
viable quantities. Initially the area is drilled on a 100m x 200m
grid (probable resource). If sufficient mineral is found a more
detailed drilling program is conducted to upgrade to a proven
resource status.
Sample holes are drilled on
a 50 x 100m grid across area.
Drill holes are taken down
to basement clay/rock (up
to 250m). Samples are taken
on 3m interval for total heavy
mineral volume.
Mineral samples taken and delivered to
the North Stradbroke Island laboratory
THE SAND MINING PROCESS
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LABORATORY ANALYSIS
FINDING
THE
MINERAL
Samples are analysed by the
laboratory on North Stradbroke
Island. The data is used for
ore-body modelling to identify
the path of the mine, which
maximises mineral production.
This initial mine path is then
adjusted taking into account
the further information gathered.
Laboratory analysis is also
utilised at the end of the mining
process to ensure the quality of
the mineral sands before they are
transported to Pinkenba.
OVERVIEW
laboratory analysis
DETAILS ON LABORATORY ANALYSIS
FINDING
THE
MINERAL
The 300gram sample is split
into 100g lots for analyses
Sample washing removes fines
(clay particles called slimes)
LABORATORY ANALYSIS
FINDING
THE
MINERAL
Drying to remove water
(samples must be in dry weight)
Lithium Silico Tungstates (LST) separation.
Separates the heavy mineral fraction from
the lighter sand using the LST solution.
LABORATORY ANALYSIS
FINDING
THE
MINERAL
LST continues (fluid and sand
mix added to the funnel)
Releasing LST mixture with
heavy mineral contained
LABORATORY ANALYSIS
FINDING
THE
MINERAL
Removing LST from sand (LST is reused)
LABORATORY ANALYSIS
FINDING
THE
MINERAL
Removing LST from sand continuing (LST is reused)
LABORATORY ANALYSIS
FINDING
THE
MINERAL
Dry material now devoid of LST, ready for analysis.
THE SAND MINING PROCESS
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PRE-MINE STUDIES
PREPARING
FOR
MINING
Before mining can commence various surveys are conducted
to provide information for planning, monitoring, environmental
management and rehabilitation.
Pre mine feasibility studies look
into the economic parameters of
the various proposed operating
methods and mine paths to
determine which would be the
most profitable method of
extraction given environmental
and socio-economic
considerations. This study is
usually done in parallel with the
environmental studies as they
feed into each other.
Pre-mine survey undertaken at
Yarraman in 1996.
MORE INFORMATION
environmental and pre-mine studies
ENVIRONMENTAL STUDIES
PREPARING
FOR
MINING
These studies provide pre-mine baseline studies of key environmental aspects
of the operation and assess potential impact on the existing environment.
Data collected in an
environmental survey include:
• Existing topography
• Vegetation studies
• Fauna studies to determine
the character, composition and
diversity of terrestrial, vertebrae
and invertebrate fauna.
• Soil studies to identify depth,
type, nutrient status and
volume of soils present.
• Hydrological data
This baseline data is necessary for
planning, monitoring, environmental
management and rehabilitation
requirements to minimise future
environmental impacts.
Click on the box above to view a video clip on
Environmental Studies and Pre-Mine Planning
THE SAND MINING PROCESS
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PLANNING
PREPARING
FOR
MINING
Project planning is the detailed
planning phase and involves the
development of the Life of Mine Plan
and inclusion of the new project in the
Plan of Operations. This would
include setting the final mine path,
developing clearing and stripping
schedules, infrastructure planning
and location, planning for water
supply requirements and finalising
tailing placement and landform
reconstruction plans
and rehabilitation schedules.
Community consultation is also undertaken with
community groups in the mine planning phase.
These studies also include a socio-economic component.
THE SAND MINING PROCESS
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CLEARING AND TOPSOIL STRIPPING
PREPARING
FOR
MINING
Prior to mining bulldozers
are used to clear the
vegetation ahead of the
mine face. The vegetation
is stockpiled then used in
post-mining rehabilitation
or burned. The topsoil is
also removed from the
mine path and stockpiled
for use in the rehabilitation
process.
Click on the image above to view a video
clip on Clearing and Topsoil Stripping
THE SAND MINING PROCESS
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DREDGE MINING
MINING
Mining is by dredge floating on an artificial freshwater pond.
This method allows large volumes of sand in a slurry form to be
pumped to the plant in a cost efficient manner. This is necessary
because the minerals CRL mines comprise less than 1% of the sand
mass. The mines each process around 3 500 tonnes of sand an hour.
The dredge constantly extracts
material from the front of the
pond, while reject material is
being placed at the rear. This
allows the mining operation to
move through the landscape at
approximately 1km per year.
A dredge and concentrator at Enterprise Mine
THE MINING PROCESS
Click on the box below to view a video clip that outlines the Dredge Mining Process.
MINING
DREDGE MINING
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MINING
Direction of travel
3. Concentrator
1. Dredge
2. Water Management
and Dredge Mining
THE DREDGE
MINING
As the dredge mines, the face
is undermined and will slowly
collapse into the water to be
processed. The dredge is fitted
with a water canon, which fires
a high-pressure jet of water to
break up any material, which
remains in chunks in the face.
The spud is used to anchor the
dredge at a fixed pivot point,
allowing the cutter head to make
sweeps across the mine face.
An auxiliary spud is carried at
the back of the dredge in case
the working spud should break.
Spuds are around 19 metres
long and 70cm in diameter.
CROSS SECTION
the dredge
A dredge at Enterprise Mine
CROSS SECTION OF THE DREDGE
MINING
MORE INFORMATION
the cutter
THE ROTATING CUTTER
MINING
At the front of the dredge a submerged
rotating cutter operates 12-15 metres
below the surface of the pond.
It loosens the sand and extracts the
minerals, which is pumped through
pipe lines to the concentrator at a rate
of approximately 3 000 tonnes per hour.
DREDGE MINING DIAGRAM
A diagram of the Rotating Cutter.
A picture of the Rotating Cutter.
WATER MANAGEMENT AND
DREDGE MINING
MINING
Water management bores
and spears are installed
alongside the mine path for
groundwater management.
This allows CRL to prevent
negative impacts such as
inundation of low lying
areas as well as enabling
some water passing
through the base of the
pond to be reused.
The water level in the
dredge pond is maintained
where necessary by
pumping water from fresh
water swamps on the
island.
Click on the image above to view a video clip on
water management during Dredge Mining.
DREDGE MINING DIAGRAM
THE CONCENTRATOR
MINING
The concentrator cleans the
sand and seperates the minerals
from the bulk of the sand tailings,
which is known as quartz. It then
begins the separation process
of the sand minerals into zircon
and an ilmenite and rutile mix.
Two main processes are used
including spiral separation and
Wet High Intensity Magnetic
Separators (WHIMS).
FLOW CHART
the concentrator
The Concentrator
FLOW CHART OF THE CONCENTRATOR
Click on each step below for detailed information on the Concentrator processes.
MINING
MINERAL CONCENTRATING PLANT (FLOATING)
4
3
1
2
THE TROMMEL
MINING
The dredge feeds directly
in to the trommel.
The trommel is a large rotating
drum, which contains mesh
screens to remove debris such
as roots and rock-like material
from coming from the dredge.
Inside the Trommel
The Trommel Screen
FLOW CHART
the concentrator
Replacement screens for the Trommel
THE SURGE BIN
MINING
The cleaned slurry from
the trommel is pumped to
the surge bin before being
passed to the rougher mill.
The surge bin allows the
fluctuations in head feed
from dredge to be offset,
so that material can be
fed to the spirals at a
constant rate. The slurry
contains about 1% heavy
minerals and 99% silica
(reject sand).
Clean Slurry travelling to the surge bin.
FLOW CHART
the concentrator
THE SPIRAL CIRCUIT
MINING
The Spiral Circuit is made up of two
sections, the Rougher Mill and the
Cleaner Mill. Both sections extract
heavy minerals from sand slurry.
In the concentrator, a gravity
separation process using a series
of water fed spirals extracts the
heavy mineral sands comprising
rutile, zircon and ilmenite.
MORE INFORMATION
spiral circuit
The Spiral Circuit inside the Concentrator
As the sand flows down the water-fed fibreglass spirals, heavy mineral
collects on the inside and lighter minerals are swept to the outside.
MINING
The rougher mill contains over
1200 spirals to separate the heavy
minerals from the residue sand.
The cleaner mill contains a further
172 spirals which process the
concentrate to 98% mineral.
Cross Section
of the Spiral
FLOW CHART
the concentrator
Photograph showing a close-up of the
spiral. If you look closely you can see
the darker minerals forming on the
inside of the spiral.
WET HIGH INTENSITY MAGNETIC
SEPARATORS (WHIMS)
MINING
After gravity separation, the heavy mineral concentrate is pumped
across wet high intensity magnets (WHIMS). The magnetic separator
extracts the Ilmenite, which is magnetic, from the Rutile and Zircon,
which are not. The separate mineral concentrates are pumped through
pipelines to stockpiles at the edge of the mine site.
CROSS SECTION
the WHIMS
Photograph of one of the WHIMS
CROSS SECTION OF THE WHIMS
MINING
MINING
As the dredge pond
advances, the residue
sand containing mostly
quartz is pumped behind
the concentrator into the
previously mined dredge path.
Information collected in
pre-mine surveys is used to
reconstruct landforms similar
to the pre-mining landforms.
These images show the existing mine path,
once the dredge has been through.
ON-SITE STOCKPILE
MINING
ON-SITE CONCENTRATE STOCKPILE AREA
The separate mineral concentrates
are pumped through pipelines to
stockpiles at the edge of the
mine site.
Click on the diagram above for more information
about On-Site Stockpiles
ON-SITE STOCKPILE
MINING
Stockpiles of the separated minerals are formed from the pipes.
Illmenite
and Rutile
Loaders are used to fill trucks (25 tonne
capacity) with concentrate from stockpiles,
for transport to a loading facility in Dunwich.
Zircon
THE SAND MINING PROCESS
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REHABILITATE MINE SITE
AFTER
MINING
CRL restores, on average, 75 hectares of their leases on North Stradbroke
Island each year and have progressively rehabilitated more than 4 000 hectares
of land since 1966. There are 3 main stages in the Rehabilitation Process.
THE SAND MINING PROCESS
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TRANSPORT MINERAL
PROCESSING
THE LOADING FACILITY AT DUNWICH ON NORTH STRADBROKE ISLAND
Every week CRL transports, on average, five 1,800-tonne loads of mineral
concentrates by barge from North Stradbroke Island to the dry mill located at
Pinkenba, near the mouth of the Brisbane River, for final separation. Travelling
from NSI across Moreton Bay to Brisbane takes four hours.
DUNWICH CONCENTRATED LOADING FACILITY
THE SAND MINING PROCESS
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MINERAL PROCESSING
PROCESSING
CRL has a dry mill at Pinkenba near the Gateway Bridge to further separate
the heavy minerals. A crane and bucket is used to pick up the mineral and
to feed the dry mill.
Minerals are unloaded for further
processing at CRL’s Pinkenba Plant
OVERVIEW final mineral
separation process at Pinkenba
Click on the map above for a better view
of Google maps
FINAL MINERAL SEPARATION
PROCESS AT PINKENBA
PROCESSING
Click on each of the
processes to find out
more about the Mineral
Separation at Pinkenba
SPIRAL CONCENTRATOR
AND WET TABLES
PROCESSING
In the Dry Mill the mineral concentrates
are again passed over spirals to remove
residual sand and then over 'wet tables'
to discard quartz and light heavy minerals.
Fine particles are removed in the wet
concentration steps and pumped to a
small dam. Water from this dam is
recycled when the fines have settled.
In the Dry Mill, concentrates are dried in
a kiln and electrostatically separated into
conductors (rutile and some residue
ilmenite) and non-conductors (zircon).
FLOW CHART
mineral separation process
ZIRCON WET PLANT
PROCESSING
Non-conductors from
the rutile separation plant
are sent down a bank of
ten spirals and eight wet
tables to separate more
middlings material. Wet
tables provide another
means of using gravity
to discard quartz and
light heavy minerals
(middlings). Fine particles
are removed in the wet
concentration steps and
pumped to a small dam.
FLOW CHART
mineral separation process
ZIRCON SEPARATION PLANT
PROCESSING
The kiln dried zircon wet
plant product is separated
using electrostatic
separation, followed by
magnetic separation. The
final traces of conductors
are cleaned from the
zircon using high tension
roll separators and
induced roll magnets.
FLOW CHART
mineral separation process
HIGH TENSION ROLL SEPARATORS
PROCESSING
High-tension roll separators are used
to perform electrostatic separation
of conductors and non-conductors.
Mineral sands are fed at
predetermined rates near the top of
an earthed rotating roll and carried
into the field of influence of a charged
ionising electrode. All particles acquire
a charge from the field. As the mineral
grains move out of the field of
influence, the conductor grains lose
their charge to the earthed roll and
are thrown from the roll surface by
centrifugal force. The non-conducting
grains adhere to the rotating roll and
pass an AC wiping electrode, which
negates their charge and the grains
begin to drop off the roll. This
discharge is completed by
a tensioned brush.
FLOW CHART
mineral separation process
RUTILE SEPARATION PLANT
PROCESSING
Mineral concentrates are dried in a kiln and electrostatically
separated into conductors (rutile and ilmenite) and non-conductors
(zircon). The rutile is cleaned electrostatically, then passed
over magnets to remove ilmenite and other magnetic minerals.
Non-conductors are fed to the zircon wet plant.
FLOW CHART
mineral separation process
ILMENITE UPGRADING PLANT
PROCESSING
Ilmenite extracted from
NSI contains chromium
at a level unacceptable
for pigment production.
Chromium causes
yellowing of the white
titanium dioxide pigment.
CRL’s ‘Ilmenite Upgrading
Plant’ separates high
chromium ilmenite with
the use of magnets since
this fraction demonstrates
greater magnetic
susceptibility.
FLOW CHART
mineral separation process
THE SAND MINING PROCESS
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SHIP TO CUSTOMERS
PRODUCT TO
FINAL
CUSTOMERS
The mineral is packaged in 25kg, 42kg, 1 tonne, 2 tonne bags, and
loaded directly into 21 tonne containers. The full containers are trucked
to container terminals at Fisherman's Island for shipment overseas.
A bulk shipment varies from 3 000 to 39000 tonnes and is loaded at a rate
of 1 400 tonnes per hour. The products are shipped to over 33 countries.
It takes about a month to ship mineral from Brisbane to the United States
and two weeks from Brisbane to Japan.
THE SAND MINING PROCESS
Click on each image for information about each stage of the sand mining process
CONSUMERS USE FINAL PRODUCT
PRODUCT TO
FINAL
CUSTOMERS