Hillgrove Project Overview

The Hillgrove Project is located approximately 30km from Armidale in New South Wales. Historic mining activity commenced at the site in 1857 and ceased in 1921 and recommenced in 1969.

Since 2004, over $180 million has been invested in underground development, surface infrastructure and processing plant by Straits Resources Limited (2004 to 2009) and most recently by the current owner, Bracken Resources Pty Ltd (“Bracken”) which acquired Hillgrove from Straits in 2013 for $33.2 million (plus the replacement of $3.9 million in environmental bonds provided by Straits).

Hillgrove was placed on care & maintenance in 2016 due to low prevailing antimony prices.

 

Figure 1 Hillgrove Gold-Antimony Project Location

 

Figure 2 Hillgrove Gold-Antimony Project Site, showing processing infrastructure and layout

 

Hillgrove Infrastructure

Since 2004, there has been significant investment, totalling over $180 million at Hillgrove, focussed on the processing plant, underground (UG) mine infrastructure and site infrastructure, but extending to other facets of the Project.

The site includes a 250ktpa capacity processing plant currently on active care & maintenance comprising a selective flotation circuit (capable of producing antimony-gold and refractory gold concentrates), an antimony leach/SXEW/refining & casting plant, a gold cyanide leach circuit & gold room and a pressure oxidation circuit.

The site also has a first aid/mine rescue centre & UG capable ambulance, plus on-site stores with ~ $2.2 million worth of stock and associated maintenance, administration buildings and laboratory/on site assay facilities.

A fully HDPE (high-density polyethylene) lined modern tailing storage facility which was constructed in 2006, and has approximately 2 years of production storage capacity.

 

Figure 3 Hillgrove Gold-Antimony Project – Key Surface Infrastructure

 

Hillgrove currently has a care & maintenance workforce of 5 people. When previously in operation, the site was a residential site, with the workforce living in Armidale. The total workforce was approximately 120 people, with UG mining carried out on an owner-operator basis utilising a comprehensive fleet of UG mining equipment which remains on site.

Hillgrove is connected to a 66kV power line and power is supplied to site via a 11kV step down transformer. Water is sourced locally and there is a reverse osmosis/microfiltration water treatment plant on site enabling treated site water to be discharged.

 

Hillgrove Mineral Field

There is a current a material high-grade Mineral Resource at Hillgrove including:

  • Mineral Resource of 2.8Mt @ 5.1 g/t Au & 1.7% Sb (7.5 g/t Au Eq.) (459Koz gold & 48Kt antimony), reported in accordance with the 2012 JORC Code; in addition to a
  • Mineral Resource of 3.9Mt @ 4.7 g/t Au & 1.3% Sb (597Koz gold & 50Kt antimony), reported in accordance with the 2004 JORC Code, with potential to convert to Mineral Resources reported in accordance with the 2012 JORC Code

The Mineral Resource is contained within 6 key hubs in the Hillgrove Mineral Field:

1. Metz Centre

  • Syndicate largely developed
  • 3rd largest gold production centre in field
  • Sunlight and Blacklode contain high-grade free and refractory gold in quartz breccia systems
  • Open at depth

2. Bakers Creek

  • Largest gold production centre in field
  • Deepest workings in Hillgrove Field

3. Brackins Spur

  • Located on southern end of Eleanora structure
  • Gold-antimony-tungsten resource – open all directions

4.Eleanora/Garibaldi

  • 2nd largest gold production centre in field
  • Mined since 1880, with modern mining undertaken from 1969-2002
  • Total strike length >8km, open all directions

5. Freehold

  • Moderate gold production
  • Not targeted by modern exploration
  • Open at depth

6. Clarks Gully

  • Recent discovery (~1990)
  • Partially mined (oxide gold) in 1994/1995
  • Open at depth

 

Hillgrove Mineral Field

 

Production

The previous operator invested over $40 million in upgrading and recommissioning Hillgrove with production of refractory gold concentrate and antimony-gold concentrate commencing in 2014. Hillgrove operated from 2014 to 2016, until is was placed on care & maintenance due to low prevailing antimony prices.

Refractory gold and antimony gold concentrate recoveries and concentrate grades

 

Recoveries

Concentrate Grades

Refractory gold concentrate

35-50% gold

30-60 g/t gold

Antimony gold concentrate

85-90% antimony

25-40% gold

55-60% antimony

15-25 g/t gold


Concentrates produced were trucked in 1 tonne bulks bags to the Port of Brisbane and the concentrates were then exported to purchasers located in China and the USA.