Mining and Processing

Mining

The ore body is accessed through a portal at the bottom of a box-cut.  A decline (5m x 5m) provides access to the ore body, ramping down at 1:7m which will reach 2.8 km from the portal.

The Angas orebody is mined using bench stoping with progressive fill. The rock is drilled and blasted from vertical stopes which are later backfilled for stability.  The mine Levels are 20 vertical metres apart and the current design depth is approximately 400m below surface.

The majority of stope production is carried out using teleremote loading. 

Forty-tonne articulated dump trucks haul the ore to a surface stockpile ready for processing.

Stoping Diagram- click to enlarge

Processing

The ore is initially crushed to 100 millimetres in diameter and then transferred to a grinding mill where it is ground to 80% passing 103 microns.  Treatment is by conventional flotation with the production of two commodities: a zinc-rich concentrate; and a lead-copper-gold-silver concentrate.

During flotation, the crushed and ground ore particles are combined with water to produce a slurry.  Next, chemicals are added to make the valuable minerals hydrophobic.  Air is pumped into the slurry and the zinc and lead-precious metals particles attach to the rising air bubbles. Adding different chemicals at specific rates separates the minerals into two different concentrates.  The zinc and lead bearing material floats to the surface and is recovered using reagents which allows the valuable materials to be separated into two concentrates. 

The concentrates are filtered and dried and temporarily stored on site in closed sheds awaiting road transport in covered B-double trucks. The concentrates are transported from site on weekdays only. The zinc is trucked to the Port of Adelaide for export to Asian markets.  The lead-copper-silver-gold concentrate is transported to the Port Pirie smelter for further refining.

Residue from the flotation phase is thickened to 70% solids and pumped to a tailings storage facility double lined with 1.5 mm high density plastic (HDPE) from which water is recovered and recycled back into the operation.

Angas Processing Schematic- Click to enlarge image