The Mindarie Mineral Sands Project is located approximately 150 km east of Adelaide in the Murray Mallee region of South Australia. The project was originally developed by Australian Zircon Limited in 2006-7, with production commencing in April 2007 and continuing until September 2009 when the company went into administration.
In June 2011, a Joint Venture (JV) was formed between majority partner (65%) Guangdong Orient Zirconic Ind Sci and Tech Co., Ltd. (OZC) and Australian Zircon NL (AZC). The objective of the JV was to redevelop and recommence mining operations at Mindarie. The joint venture established Murray Zircon Pty Ltd as a new private company, and vended all project related assets and outstanding rehabilitation liabilities into the Company.
Murray Zircon (MZ) assembled a management team and embarked on the redevelopment of the Mindarie Project in August 2011. Redevelopment activities included completing outstanding rehabilitation of previously mined areas, refurbishing the primary concentrator plant (PCP), acquiring a new mine slurry unit, purchasing new grid powered slurry booster skids, installing additional electrical infrastructure, securing a new mining permit, and constructing a new mine.
As part of its commitment to earning its social license to operate in South Australia, Murray Zircon accepted the liability of completing outstanding rehabilitation of approximately 4 kilometers of previously mined sections of the Mindarie ‘A2” and ‘C’ strand lines. The objective of the rehabilitation was to return the land to its previous land use as broad acre farming (cropping).
Murray Zircon’s mine rehabilitation effort began in August 2011 following consultation with local landowners, community leaders and regulatory authorities. Initial attention was focused on solar drying of tailings slimes pools. Once the slimes were sufficiently stabilised and returned to the bottom of the mine void, stockpiled overburden was used to cover the tailings as backfill to original elevation, followed by replacement of subsoil and topsoil. The final placement of topsoil was completed in March 2012, followed by the planting of a cover crop in April/May.
|Rehabilitation of Previously Mined Land – Milestones|
|Drying and stabilisation of slimes||Completed November 2011|
|Overburden replacement||Completed December 2011|
|Sub-soil replacement||Completed February 2012|
|Top-soil replacement||Completed March 2012|
|Planting cover crop||Completed April/May 2012|
The measure of success for rehabilitated mine land is a demonstration of crop yields following rehabilitation. Environmental regulations in South Australia require an independent determination that crop yields are equal to or greater than crop yields in adjacent unmined areas, for 3 out of the 5 years following rehabilitation. By the end of December 2013, Murray Zircon had demonstrated crop yields on the rehabilitated mine areas that were deemed to be as good or better than on unmined areas for 2 of the required 3 years.
Concurrent with mine rehabilitation efforts, Murray Zircon embarked on the preparation of a Program for Environmental Protection and Rehabilitation (PEPR) application for approval by the Resources Division of Primary Industries and Resources South Australia (PIRSA). The objective of the PEPR was to secure regulatory approval to recommence mining and production of heavy mineral concentrate.
As a result of the Company’s successful mine rehabilitation efforts, and its continuing positive community consultation process, the Department of Manufacturing, Industry, Trade, Resources and Energy (DMITRE; formerly PIRSA) approved Murray Zircon’s PEPR application in April 2012; less than one year from the formation of the company.
In conjunction with the PEPR application and approval process, Murray Zircon finalized plans for the redevelopment of the Mindarie Project including detailed mine planning and refurbishment of the wet concentrator plant (WCP) and associated slurry pumping system between the mine and WCP. Following approval of the PEPR, project redevelopment activities were fast-tracked.
Initial redevelopment activities included the removal and storage of topsoil and subsoil from the initial box cut area of the new mine on the Mindarie C West mineral sand ‘strand’ deposit and installation of electrical infrastructure (power lines) out to the mine.
Milestones achieved to finalise the redevelopment of the project include:
Mineral sands ore is mined at Mindarie using dry mining techniques. Topsoil and subsoil are first removed using tractors and landplanes and stockpiled along-side the mine path for post-mining rehabilitation. Overburden is removed using scrapers. Overburden is either stockpiled or returned directly to mined-out areas. Ore is mine using dozers to push the ore to temporary stockpiles adjacent to the Mine Slurry Unit (MSU) located within the mine. Dozer pushing blends the ore in advance of it being fed to the MSU hopper by front-end loader.
In the MSU, the ore is screened of oversize rocks and then mixed with water to slurry the ore for pumping in pipelines to the Wet Concentrator Plant (WCP). At the WCP the ore slurry is rescreened to remove smaller rocks before it is pumped through cyclones to remove fine clays and silts before being pumped over spiral classifiers to recover the heavy minerals.
Following removal of the heavy mineral components from the ore slurry, residual sands and thickened clays/silts are then pumped back to the mine as a tailings slurry, where it is treated with a flocculent and returned to the bottom of the mine and allowed to dewater and consolidate. After the tailings are sufficiently dewatered and stabilized, overburden is placed over them and the mine void backfilled back to its original overburden elevation before subsoil and topsoil are replaced to the original surface contours.
The mining process at Mindarie is known as a ‘moving-hole’ concept since the mine void advances in the direction of mining as new ore is exposed and tailings is simultaneously covered at the back of the mine. This process requires rapid tailings dewatering and stabilization and covering with overburden; or rapid mine rehabilitation. Murray Zircon has successfully demonstrated rapid mine rehabilitation is achievable.
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Heavy mineral concentrate (HMC) recovered from the ore slurry through the WCP spiral circuits is screened and then pumped through dewatering cyclones where the HMC drops into piles and is allowed to drain of free water. The HMC (typically 80-90% heavy minerals) is then stockpiled on an open pad designed to allow any remaining water to be recovered and recycled to the WCP.
Moist HMC is later loaded onto trucks and transported to Port Adelaide where it is loaded into shipping containers and shipped (exported) to China for further processing. In China, the HMC is separated into individual heavy mineral products of zircon, ilmenite, rutile and leucoxene.
Below are Murray Zircon’s statements of Ore Reserves and Mineral Resources updated effective 1 Jan 2016 in accordance with the 2012 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’.
Mining and HMC production was restarted by Murray Zircon at Mindarie in 2012. Following successful re-commissioning of the project to full name-plate capacity, operations continued successfully through March 2015. However, due to continually falling commodity prices throughout this operating period, a decision was made by the Board of Directors to discontinue mining operations with the completion of mining at Mindarie C East, and to place the project on care and maintenance until such time as mineral sands commodity prices sufficiently rebound.