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De Grey Mining completes ore sorting test work from its Toweranna Gold deposit in WA

Last updated: 23:40 06 May 2019 EDT, First published: 09:40 06 May 2019 EDT

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Laser sorting products from Toweranna test work

De Grey Mining Limited (ASX:DEG) has confirmed positive results from ore sorting test work undertaken on geological samples from the Toweranna gold deposit within its wider Pilbara Gold Project in Western Australia.

Mineralised quartz and sulphide vein material was efficiently separated from non-mineralised host granitoid and sediments using single-pass laser sorting at a coarse feed size of 20-100 millimetres.

The test work, which was undertaken by TOMRA Sorting Pty Ltd, was completed on five distinct geological rock types from a single drill hole at Toweranna.

TOMRA was requested to assess the various rock types and if feasible to demonstrate that the mineralised quartz-sulphide vein material could physically and efficiently be separated from the non-mineralised waste rock types.

READ: De Grey Mining hits bonanza gold grades up to 58.9 g/t at Toweranna deposit

The composite sample was sorted using laser scanning and a second pass of X-RAY Transmission (XRT) scanning was undertaken on the waste product to determine if any sulphide mineralisation remained.

XRT results showed there were negligible sulphide minerals remaining in the waste product.

The evaluation was set to retain any fragments with less than 5% quartz by area.

Notably, the laser scanning, which targets identification and retention of quartz veining, has accurately retained almost all fragments with any quartz veining.

Assays of the material have not been undertaken as this preliminary sampling was designed to provide only rock type characterisation.

READ: De Grey Mining in trading halt ahead of material exploration results from Pilbara Gold Project

De Grey has planned further ore sorting testing to target known mineralised intersections as well as to determine the potential increased grade through ore sorting prior to concentration.

Grade increases are expected with ore sorting as the gold is known to be almost exclusively hosted in the quartz-sulphide veins based on detailed core samples and gold results.

 Visible gold in quartz-sulphide vein

 

The company considers the results to be excellent and clearly demonstrate the potential to upgrade and concentrate the quartz-vein material prior to trucking to the proposed processing plant.

Test work results provide additional confidence that ore sorting may provide substantial added benefits through enhanced grade increases, improving future economics at Toweranna.

De Grey consideres ongoing conventional metallurgical test work, ore sorting and financial evaluation warranted.

The company's planned activities include finalising metallurgical test work on the purpose-drilled PQ core, which has been well-advanced by ALS Metallurgy.

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