Geology and Exploration History

St Dizier is a satellite open-pit tin deposit located 20km to the northwest of Zeehan. St Dizier is a tin skarn, formed by metasomatic alteration of an original dolomite unit by tin bearing fluids emanating from the Heemskirk Granite. Much of the dolomite is altered to serpentine-magnetite-calc-silicate rock flanked by shales to the south and quartzites to the north. The total meta-sediment package has the form of an east-west trending, vertically dipping roof pendant surrounded by Heemskirk Granite. The skarn consists of magnetite-serpentinite-cassiterite-schoenfliesite-scheelite-bismuthinite. Tin mineralisation is zoned with dominantly cassiterite in the west and increasing amounts of schoenfliesite and other tin species to the east.

 

43 historic diamond drill holes for 7,309m have been completed at St Dizier over a number of campaigns by different operators. Stellar has completed a further 3 confirmatory diamond drill holes for 317m at St Dizier

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St Dizier Interpretive Geology and Drilling

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Plan View of St Dizier Geology

The Indicated Resource at St Dizier includes the West and Central Lodes. The bodies crop-out at the surface and strike east-west over a distance of 400m. They dip vertically to a depth of 200m from the surface (in the case of Central) and vary in width from 3m to 40m. Higher tin grades occur between the surface and a depth of 70m in the Central Lode and grades are higher nearer to the surface making the deposit attractive as a potential low-cost open pit development. The smaller Western Lode could also potentially be considered for open pit mining but was not included in the 2019 Scoping Study.

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Cross-Section 345,150mE, Central Lode, St Dizier

Resource

A total Indicated and Inferred Mineral Resource for St Dizier of 2.3mt @ 0.61% Sn (13,786t of contained tin) at a cut-off grade of 0.3% Sn has been defined in accordance with the JORC Code 2012 by technical consultant, Resource and Exploration Geology, in March 2014. The Indicated component of the resource is 1.2mt grading 0.69% tin, 87% of which is in the form of cassiterite. There has been no material change to assumptions since the resource estimate was completed in 2014.

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St Dizier Mineral Resource Statement (JORC 2012), March 2014

Mining

A mining study on the St Dizier Deposit completed by Polberro Consulting in July 2015 forms the basis of the mining assumptions used in the Hemskirk Tin Project 2019 Scoping Study. The Polberro St Dizier mining study included; pit optimisation, open pit mine design, consideration of geotechnical factors, bench geometry, mine production rate and mining operating and capital costs.

The Polberro St Dizier mining study focused purely on part of the Central Lode Indicated Resource and determined that an open pit mining method which is well suited to the Central Lode mineralisation as it crops out at the surface, has its highest grades within 50m of the surface, occurs as multiple lenses over widths of 3m to 40m and is surrounded by relatively competent wall rocks. It is also the lowest cost mining method available for the style of mineralisation.

Key results from the Polberro St Dizier mining study, used in the 2019 Scoping Study include:

  • In-pit diluted indicated mineral resource of 409,179t @ 0.90% Sn with an average strip ratio of 4.7:1 after application of 10% mining dilution and 95% mining recovery factors
  • 100% Indicated Mineral Resource
  • Mining capital costs of A$3.3m for drainage diversion, pit development and construction of a waste which can be completed within 3 months
  • Mine closure capital cost of A$0.5m
  • Contractor operated mining costs estimated at A$26/t ore mined inclusive of waste removal,
  • Trucking cost of A$5/t for trucking St Dizier ore a distance of 20km to the processing plant at Heemskirk
  • The accuracy of the mining operating cost and capital cost estimates was ±35%

The Heemskirk Tin Project 2019 Scoping Study includes mining from the St Dizier satellite tin deposit which will be mined as an open pit mine and processed in the Heemskirk plant during the last year of the project.

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Long Projection St Dizier Tin Deposit

Metallurgy

St Dizier ore is similar in complexity to that at Upper Queen Hill. Stage 1 test work on diamond drill core from St Dizier has been undertaken by ALS Metallurgical Laboratory in Burnie and supervised by Worley Parsons. The test work showed the following outcomes:

  • Mineralisation in the sample was quite variable and provides a wide range of responses
  • High tin losses to magnetite, slime and tin float tails resulted in overall recovery of 43%
  • Gravity concentrate tin grade of 55% is possible through pre-gravity sulphur removal
  • Tin float grade could be significantly upgraded by optimising deslime, talc management and acid leaching of concentrate
  • Stage 2 optimisation has the potential to increase tin recovery up to 50% into a 50% tin in concentrate product