Invincible Mine, Glenorchy, Queenstown-Lakes District, Otago Region, New Zealandi

Regional Level Types
Invincible Mine	Mine
Glenorchy	- not defined -
Queenstown-Lakes District	District
Otago Region	Region
New Zealand	Country

Abandoned gold mine.

The Invincible Mine is 18 kilometres north of Glenorchy in the Rees Valley. A steep one hour walk will take visitors to the locked mine entrance, tailings, waterwheel remains, and a unique set of seven berdan pans. In the valley below is the Otago Pyrites Saving Company's buddle, a science fiction looking contraption in a forest clearing, used to separate gold from the tailings brought down from the mine.

The underground mine was operated by the Invincible Quartz Mining Company from 1882, until they lost the reef in 1887. The battery yielded 325 ounces from one crushing, and worked 24 hours per day, crushing 90 tonnes of ore per week. Around 7500 ounces of gold in total was recovered in the mine's history, at an average grade of 30 gr per tonne. Efforts to re-open the mine in 1902, 1912, and 1922, all came to nought. The underground workings have collapsed.

The Invincible Reef occupies a near vertical high angle reverse fault, cross-cutting regional schistosity, which regionally dips west by 50 degrees. The reef is on the eastern limb of the Miocene aged Earnslaw Synform. The host schist contains quartz, albite, muscovite, chlorite, epidote, titanite, graphite, actinolite, pyrrhotite, and calcite.

The reef trends north-east to south-west, and dips steeply south-east. The underlying Aspiring Terrane is the significant source of the mineralising fluids and metals. This occurred in the latter stages of metamorphism, and is the earliest recognised gold bearing vein system, in the regionally extensive Otago Schist.

Gold occurs as blebs in quartz. An up to one metre alteration zone surrounds the lode, marked with sulphides, although little alteration other than the recrystallization of chlorite. The mineralised vein material filling the fault zone consists of quartz, albite, muscovite, chlorite, calcite, pyrite, arsenopyrite, and minor gold. The minerals have been strained and recrystallised during ductile deformation.

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