King Island Scheelite is redeveloping the historic Dolphin tungsten mine on the Kings Island in Tasmania, Australia. Image courtesy of King Island Scheelite.
Dolphin tungsten mine is expected to produce 3,500t of WO3 concentrate a year. Image courtesy of King Island Scheelite.
The proposed Dolphin tungsten project conducted underground and open-cut mining operations previously. Image courtesy of King Island Scheelite.

Dolphin tungsten project is an open-cut mine being developed on King Island, Tasmania, Australia. King Island Scheelite is the project owner and operator.

Estimated to cost $64.8m (£50.6m), the project involves the redevelopment of the historic Dolphin mine, which previously employed open-cut and underground methods to produce 9.7Mt between 1917 and 1992.

The proposed new open-cut mine is anticipated to process 400,000tpa of ore and produce 3,500t of WO3 concentrate a year during its estimated eight years of mine life.

The King Island Council and the Tasmanian Environment Protection Authority (EPA) approved the project development in October 2017. King Island Scheelite completed the project feasibility study (FS) in June 2019.

The developer aims to achieve financial closure for the project in mid-2019 and start production in 2021.

Dolphin tungsten project location and geology

The Dolphin tungsten mine is located on the mining lease 1/M2006, near the town of Grassy, King Island.

The project hosts scheelite skarn mineralisation, which is a part of the metamorphic aureole of the Carboniferous Grassy Granit.

The mineralisation at the project is contained within a 100m-200m thick sequence of complex skarn, which is made up of two main horizons, namely B and C Lens. The deposit is hosted within C Lens, which hosts garnet hornfels, pyroxene-garnet hornfels, and banded pyroxene-garnet hornfels.

Ore reserves at Dolphin tungsten project

The probable ore reserves at the Dolphin tungsten mine were estimated to be 3Mt graded at 0.73% WO3, as of June 2019.

Mining at Dolphin tungsten project 

The tungsten project is proposed to use a conventional open-cut mining method involving drilling and blasting. The mined ore will be transported using hydraulic excavator and trucks.

The mining fleet will include a 140t CAT6015B backhoe excavator, a 50t CAT excavator, and three CAT775G dump trucks for ore loading and hauling. The ancillary fleet will consist of a CAT D10 bulldozer, a CAT D9 bulldozer, a CAT grader, CAT 996FE Loader, and a 5000l Isuzu utility truck.

Processing at Dolphin tungsten project

The project will include a gravity processing plant and a small flotation processing plant to produce gravity concentrate and flotation concentrate, respectively. The final gravity concentrate is expected to have a grade of 65% WO3, while the flotation concentrate will be graded between 30% and 45% WO3.

The ore will be crushed in two stages, stored in a fine ore stockpile, followed by crushing in a fine vertical shaft impact crusher.

The crushed ore will be passed through the gravity circuit and the resultant tailings forwarded to the flotation circuit for processing.

The produced concentrate will be sold in the Ammonium Paratungstate market.

Off-take details

King Island Scheelite has secured an off-take agreement with Wolfram Bergbau und Hutten, a tungsten powder provider based in Europe, for the sale of 140,000mtu of WO3. Wolfram, a wholly-owned subsidiary of Sandvik, has agreed to purchase tungsten concentrate produced from the mine for four years.

Dolphin Tungsten project infrastructure 

The project is located close to the Grassy Port, which is capable of hosting 5,000t ships.

Raw water will be collected from the existing Lower Grassy Dam, while potable water is proposed to be sourced from the local scheme supply and stored in tanks.

Power supply for the project will be secured from the existing grid power from Hydro Tasmania, the local provider. A proposal is also made to use four diesel-powered generators on lease for the processing plant and the mine site.

Other infrastructure will include a tailings storage facility, site accommodation facility, site office, and heavy vehicle workshop. 

Contractors involved

KIS prepared the feasibility study with support from a group of consultant including Xenith Consulting, Resource and Exploration Geology, PSM, ALS, Asther, Bill Meynink, and GHD.

Other companies involved in the study were BR Design, SEMF, Pit and Sherry, Consulting Environmental Engineers, Ernst Friedlander, ARGUS, and Brendan Walpole.

Gekko Systems was engaged to conduct engineering study for the design and installation of the processing plant of the Dolphin tungsten project.