Mount Bischoff mine (Mt Bischoff mine), Waratah, Waratah district, Waratah-Wynyard municipality, Tasmania, Australia
|Latitude & Longitude (WGS84):||41° 25' 53'' South , 145° 31' 25'' East|
|Latitude & Longitude (decimal):||-41.43150,145.52383|
|Age:||382.7 ± 1.6 to 358.9 ± 0.4 Ma|
|Geologic Time:||Late Devonian|
|Köppen climate type:||Cfb : Temperate oceanic climate|
A famous old tin mine near Waratah, NW Tasmania. It was the mine the really helped opened up the west coast of Tasmania.
The Mt Bischoff mine was discovered by farmer and part-time prospector James “Philosopher” Smith in 1871, and for many years was one of the world’s richest tin mines (Groves et al., 1972). After 70 years of continuous production, the Mt Bischoff mine finally closed in 1947. Following mining ventures have mostly been small and spasmodic. Open-cut mining restarted in 2008, with a large open pit swallowing most of the old workings, except the Slaughteryard Face. Mining reserve estimates as at June 30, 2008 are 845,000t at 1.20% Sn. The ore was trucked some 50km to the mill at the Renison Bell tin mine. Mining finished in 2011 and the pit is now flooded, but exploration continues around the pit and deeper reserves are of great exploration interest.
Mt Bischoff was the first major mineral resource developed in Tasmania, with a total production of around 62,000t of metallic tin. The discovery provided the impetus for exploration of other areas of the west coast and the subsequent discovery of other mining areas such as Mt Lyell and Renison.
Precambrian quartzite, shale and dolomite at Mt Bischoff have been intruded by a radial group of Devonian quartz-feldspar porphyry dykes and breccia dykes, related to the nearby Meredith granite. Tin-base metal sulphide mineralisation accompanies these dykes, and occurs as a replacement of dolomite, as greisenised dykes, and as veins and fracture linings (Groves et al., 1972; Wright & Kwak, 1989, Halley & Walshe, 1995; Sorrell, 1997). Tin mineralisation occurs within a radius of about 1km from the summit of Mt Bischoff, and several silver-lead-antimony deposits surround the mine. Supergene zones were minor.
Dolomite-replacement mineralogy is dominated by sulphides (mostly pyrrhotite), Fe-Mg-Mn carbonates, fluorides (fluorite, sellaite), tourmalines and magnesium silicates (chondrodite, norbergite, clinohumite, phlogopite, talc and serpentine), in part as magnesian skarns and “wrigglite” (banded skarn), largely retrogressed. The highest tin grades were found within a quartz-pyrrhotite-topaz-fluorite assemblage (the most strongly altered dolomite replacement rocks) adjacent to the dykes, (now largely worked out). Dolomite-replacement mineralisation is found at the Greisen Face, where talc-pyrrhotite alteration occurs, and at the Slaughteryard Face, where quartz-pyrrhotite alteration and fluorite “nodules” occur.
Greisenised dyke rocks are characterised by a white, fine-grained groundmass of quartz and topaz, with orthoclase phenocrysts variably pseudomorphed by siderite, pyrrhotite, quartz, topaz, pyrite, fluorite and cassiterite. One of the most prominent features of Mt Bischoff is the Western Dyke, a greisenised porphyry with cassiterite both disseminated and coating joint surfaces.
Veins and Fracture Linings
Fissure lodes are a late phase of mineralisation, cross-cutting dykes and country rocks. They contain variable proportions of quartz, siderite, tourmaline, topaz, fluorite, cassiterite, wolframite and sulphides (pyrite, pyrrhotite, galena, sphalerite, chalcopyrite, bismuthinite, As-Sb-Bi sulphosalts and stannite).
More than 100 mineral species have been recorded from Mt Bischoff, particularly because of the extensive alteration and large amounts of magnesium and fluorine in the system, producing both attractive and uncommon minerals such as sellaite, franckeite, chondrodite, norbergite, wagnerite and fluoborite.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
120 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
541 - 1000 Ma
|Oonah Formation and correlates|
Age: Neoproterozoic (541 - 1000 Ma)
Stratigraphic Name: Oonah Formation and correlates
Comments: sedimentary siliciclastic; synthesis of multiple published descriptions
Lithology: Sedimentary siliciclastic
Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia).