HOW ARE MINERAL SANDS MINED ON NORTH

STRADBROKE ISLAND?

Click through the slides to view this presentation.

Follow the links in grey to view more information on the different steps involved in the mining of mineral sands.

INSTRUCTIONS FOR VIEWING THIS PRESENTATION

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

EXPLORATION DRILLING

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.

Mineral samples taken and delivered to the North Stradbroke Island laboratory

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.

FINDING THE

MINERAL

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

LABORATORY ANALYSIS

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

FINDING THE

MINERAL

DETAILS ON LABORATORY ANALYSIS

The 300gram sample is split into 100g lots for analyses

Sample washing removes fines (clay particles called slimes)

FINDING THE

MINERAL

LABORATORY ANALYSIS

Lithium Silico Tungstates (LST) separation. Separates the heavy mineral fraction from

the lighter sand using the LST solution.

Drying to remove water (samples must be in dry weight)

FINDING THE

MINERAL

LABORATORY ANALYSIS

Releasing LST mixture with heavy mineral contained

LST continues (fluid and sand mix added to the funnel)

FINDING THE

MINERAL

LABORATORY ANALYSIS

Removing LST from sand (LST is reused)

FINDING THE

MINERAL

LABORATORY ANALYSIS

Removing LST from sand continuing (LST is reused)

FINDING THE

MINERAL

LABORATORY ANALYSIS

Dry material now devoid of LST, ready for analysis.

FINDING THE

MINERAL

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

PREPARING FOR

MINING

MORE INFORMATION environmental and pre-mine studies

PRE-MINE STUDIES

Before mining can commence various surveys are conducted to provide information for planning, monitoring, environmental management and rehabilitation.

Pre-mine survey undertaken at Yarraman in 1996.

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.

ENVIRONMENTAL STUDIES

These studies provide pre-mine baseline studies of key environmental aspects of the operation and assess potential impact on the existing environment.

Click on the box above to view a video clip on Environmental Studies and Pre-Mine Planning

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.

PREPARING FOR

MINING

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

PLANNING

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.

PREPARING FOR

MINING

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

CLEARING AND TOPSOIL STRIPPING

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

PREPARING FOR

MINING

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

DREDGE 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.

A dredge and concentrator at Enterprise Mine

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.

MINING

THE MINING PROCESSClick on the box below to view a video clip that outlines the Dredge Mining Process.

MINING

DREDGE MININGClick on each step below for detailed information on the dredge mining processes

2. Water Management

and Dredge Mining

1. Dredge3. Concentrator

Direction of travel

MINING

CROSS SECTION the dredge

THE DREDGE

A dredge at Enterprise Mine

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.

MINING

MORE INFORMATION the cutter

CROSS SECTION OF THE DREDGE

MINING

THE ROTATING CUTTER

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 picture of the Rotating Cutter.A diagram of the Rotating Cutter.

MINING

WATER MANAGEMENT AND DREDGE 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

MINING

THE CONCENTRATOR

The Concentrator

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

MINING

Click on each step below for detailed information on the Concentrator processes.FLOW CHART OF THE CONCENTRATOR

MINERAL CONCENTRATING PLANT (FLOATING)

1

2

3 4

MINING

THE TROMMEL

Replacement screens for the Trommel

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.

The Trommel Screen

Inside the Trommel

FLOW CHART the concentrator

MINING

THE SURGE BIN

Clean Slurry travelling to the surge bin.

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).

FLOW CHART the concentrator

MINING

THE SPIRAL CIRCUIT

The Spiral Circuit inside the Concentrator

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.

MINING

MORE INFORMATIONspiral circuit

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.

As the sand flows down the water-fed fibreglass spirals, heavy mineral collects on the inside and lighter minerals are swept to the outside.

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

MINING

WET HIGH INTENSITY MAGNETIC SEPARATORS (WHIMS)

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.

Photograph of one of the WHIMS

CROSS SECTIONthe WHIMS

MINING

CROSS SECTION OF THE WHIMS

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.

MINING

ON-SITE STOCKPILE

Click on the diagram above for more information about On-Site Stockpiles

The separate mineral concentrates are pumped through pipelines to

stockpiles at the edge of the mine site.

ON-SITE CONCENTRATE STOCKPILE AREAMINING

ON-SITE STOCKPILE

Loaders are used to fill trucks (25 tonne capacity) with concentrate from stockpiles,

for transport to a loading facility in Dunwich.

Stockpiles of the separated minerals are formed from the pipes.

Zircon

Illmenite and Rutile

MINING

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

AFTER MINING

REHABILITATE MINE SITE

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 PROCESSClick on each image for information about each stage of the sand mining process

TRANSPORT MINERAL

THE LOADING FACILITY AT DUNWICH ON NORTH STRADBROKE ISLANDEvery 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

PROCESSING

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

MINERAL 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

Click on the map above for a better view of Google maps

OVERVIEW final mineral separation process at Pinkenba

PROCESSING

FINAL MINERAL SEPARATION PROCESS AT PINKENBA

Click on each of the processes to find out more about the Mineral Separation at Pinkenba

PROCESSING

SPIRAL CONCENTRATOR AND WET TABLESIn 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

PROCESSING

ZIRCON WET PLANT

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.

PROCESSING

FLOW CHART mineral separation process

ZIRCON SEPARATION PLANT

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.

PROCESSING

FLOW CHART mineral separation process

HIGH TENSION ROLL SEPARATORS

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

PROCESSING

RUTILE SEPARATION PLANT

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

PROCESSING

ILMENITE UPGRADING PLANT

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.

PROCESSING

FLOW CHART mineral separation process

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

SHIP TO 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.

PRODUCT TO FINAL

CUSTOMERS

THE SAND MINING PROCESSClick on each image for information about each stage of the sand mining process

CONSUMERS USE FINAL PRODUCTPRODUCT TO

FINAL CUSTOMERS