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RESOURCES Tasmania DEPARTMENTof INFRASTRUCTURE, ENERGY and RESOURCES Tasmanian Geological Survey Record 2001/08 A mineralogical field guide for a Western Tasmania and museums tour

by R. S. Bottrill

This guide was originally produced for a seven day excursion held as part of the International Minerals and Museums Conference Number 4 in December 2000. The excursion was centred on the remote and scenically spectacular mineral-rich region of northwestern Tasmania, and left from Devonport. The tour began with a trip to the Cradle Mountain National Park, then took in visits to various mines and mineral localities (including the Dundas, Mt Bischoff, Kara and Lord Brassey mines), the West Coast Pioneers Memorial Museum at and a cruise on the . A surface tour of the deposit at Mt Lyell followed before the tour moved towards . The last day was spent looking at mineral sites in and around Hobart. Although some of the sites are not accessible to the general public, this report should provide a guide for anyone wishing to include mineral sites in a tour of Tasmania.

CONTENTS Tasmania— general information Natural history and climate ………………………………………………… 2 Personal requirements ……………………………………………………… 2 General geology…………………………………………………………… 2 history …………………………………………………………… 4 Fossicking areas — general information ………………………………………… 4 Mineral locations Moina quarry …………………………………………………………… 6 Middlesex Plains ………………………………………………………… 6 Lord Brassey mine ………………………………………………………… 6 Mt Bischoff ……………………………………………………………… 6 Kara mine ……………………………………………………………… 10 Colebrook Hill, Dundas……………………………………………………… 10 Serpentine Hill–Nevada Creek– Hill, Dundas ……………………………… 11 mines, Dundas …………………………………………………… 11 mine …………………………………………………… 12 Mt Lyell mines …………………………………………………………… 13 Minerals of the Cygnet district ………………………………………………… 15 References …………………………………………………………………… 16

Tasmanian Geological Survey Record 2001/08 1 Tasmania – General Information

The of Tasmania is the smallest and most 5–16ºC in Waratah (western Tasmania) to 11–21ºC in southerly of ’s six States. It has a population of Hobart (eastern Tasmania). In winter (June to August) 473,000 and lies about 200 km south of the State of the average daily temperature range varies from about , being separated from Australia by 1–8ºC in Waratah to 5–12ºC in Hobart. Rainfall varies . The heart-shaped island is about 315 km from about 2200 mm/annum in Waratah to across and 286 km long, making it about the same size 620 mm/annum in Hobart, with falling as Ireland and a little larger than West Virginia. Much throughout the year but peaking in winter. Snow is of Tasmania is still wilderness and more than 20 per common over much of the higher parts of Tasmania in cent of the area has been listed with UNESCO as a winter but is rare in summer. World Heritage Area, in recognition of one of the world’s great natural treasures. Personal requirements Tasmania was originally named Van Diemens Land by Whenever working in the sun wear a broad-rimmed the Dutch explorer in 1642, but it was not hat and use a sun-block preparation (particularly colonised until the British started a penal colony in November to March). The ozone layer is thin and the 1803. At that time it is believed there were about 5000 Tasmanian sun may feel cool, but can burn rapidly. In Aboriginal people living on the island with a presence central and western Tasmania be prepared for snow extending back for more than 50,000 years, although and rain at any time of year, and very sudden changes most had died from various diseases within 30 years. in weather. Always take appropriate clothing — a Convict transportation ceased in 1853. Until then the warm pullover and raincoat and wear sturdy footwear. convicts had provided the main source of building An insect repellant may be useful at times. Leeches, labour in the colony and this heritage is still evident ants and snakes can be a nuisance in places and suitable throughout much of Tasmania today. The is (long and tight fitting) clothing and footwear is Hobart with a population of 193,000. Statistically, recommended for the squeamish. Hobart has half the rain of , more sun than and is warmer than Madrid. Safety equipment, including hard hats, safety glasses and sturdy boots (preferably steel-capped) should be Tasmania, like its minerals, is incredibly diverse and carried. beautiful, and we hope you will enjoy your visit.

Natural history and climate General geology Tasmania is geographically quite different to most of The is complex, with rocks of Australia, being comparatively rugged, cool and wet. most major ages, from mid-Proterozoic to Cainozoic, The State comprises one major island and numerous being represented (fig. 1). There is considerable smaller , with an area of about 64 000 km2, lying , mineralisation and hydrothermal in a belt of moisture-laden westerly winds. Western alteration in many areas (Burrett and Martin, 1989). Tasmania is largely mountainous and lies in the path of The oldest rocks are (mid to late these winds, giving it year-round rain (over 2000 mm Proterozoic) metasediments, mostly , in places). Eastern Tasmania is mostly drier, being in a dolomite and slate, with some , , rain shadow. , and . Some of these The highest Tasmanian mountain is Mt Ossa at 1617 m, rocks host major deposits (e.g. Renison and Mt and there are over 60 peaks above 915 metres above sea Bischoff), smaller --, and copper level. These peaks and plateaus are frequently snow deposits, and some magnesian ± borate . covered in winter, and some summer snowfalls occur, Thrust over these rocks in many parts of Tasmania are but there is no permanent snowline. Vegetation is mafic-ultramafic ophiolitic complexes. complex, ranging from montane (alpine heathlands) to These are now mostly serpentinised and host a wide temperate rainforest (myrtle forest), dry sclerophyll range of deposits (platinoids, , nickel, forest (eucalypt forest, including some of the world’s silver-lead-zinc, copper and gold). tallest flowering trees), sedgeland (buttongrass plains) and coastal heath. The vegetation has two main Overlying the older rocks are Late Cambrian components: an Antarctic or Gondwanaland flora (also sedimentary, volcanic and intrusive rocks, particularly represented in and South America) and the Volcanics. These are also highly an Australian flora, dominating most of Australia. mineralised, with the Mt Lyell, Rosebery, Hellyer and Tasmanian fauna is generally similar to mainland Hercules mines all being world-class base and precious Australia. deposits. Significant gold deposits also occur. Tasmania has a mild maritime to cool temperate These rocks are largely conformably overlain by climate. In summer (December to February) the to Early sedimentary sequences. average daily temperature range varies from about These host some very important gold deposits and

Tasmanian Geological Survey Record 2001/08 2 Furneaux Flinders

145° 146°

144° 148° 147° Island TASMANIA 40°

40° GEOLOGICAL FRAMEWORK

Grassy

Group

050100 km

Smithton Wynyard Beaconsfield 41° 41° Burnie Devonport Kara Scottsdale LINEAMENT

Savage River LAUNCESTON Scamander Moina Deloraine

ARTHUR

Rosebery

42° Zeehan 42° POST-DEVONIAN Queenstown

COVER ROCKS

Adamsfield

HOBART

43° 43° Elliott Tasman Bay Peninsula

South West Cape

146°

145°

148°

147° LEGEND Permo- sedimentary Middle–Late Cambrian – Early rocks, dolerite and -sedimentary Cambrian sedimentary Cainozoic sediments sequences rocks and

Devonian Middle–Late Cambrian Neoproterozoic Mt Read Volcanics

Mesoproterozoic: Late Cambrian to Early Early Cambrian allocthons: Metasedimentary rocks; Devonian sedimentary Ultramafic-mafic complexes relatively unmetamorphosed rocks; Mathinna Group (black); sedimentary rocks sedimentary rocks; Arthur and basalt Metamorphic Complex Figure 1

Tasmanian Geological Survey Record 2001/08 3 tin--bismuth, , and Pb-Zn The climate and terrain of the Western Tasmanian skarns. mineral belt impeded exploration, but prospectors trickled westwards and made some major mineral All of the preceding sequences are affected to varying discoveries in the 1870s and 1880s (particularly the degrees by the intrusion of many large and widespread deposits of tin at Mt Bischoff and copper and gold at Mt Devonian granitoids, forming and skarns and Lyell). These discoveries resulted in extensive causing the introduction or remobilisation of much of prospecting and mining operations, most of which had the above-mentioned mineralisation. ceased by the turn of the century, and nearly all by Following the granitoid intrusions and in the World War I. Some major producers have remained in Devonian, extensive fluvioglacial sediments were continuous operation for about 100 years or more, for deposited in the Late to Triassic. These example the Renison tin mine, the Mt Lyell copper rocks were intruded by numerous large Jurassic mine and the Rosebery lead-zinc mine. Mineral dolerite dykes and sills, equivalent to those in exploration continues and new discoveries are still and South . Although mostly being made (for example the , opened unmineralised, some of these rocks contain in 1996). and related secondary minerals. Partial of columnar dolerite has produced many spectacular Fossicking Areas — general and mountains. information Widespread uplift during the resulted in There are many localities within Tasmania where only limited sedimentation, although there were some interesting lapidary and mineralogical material occur, local high level alkaline intrusions (feldspathoidal including the Lord Brassey and Colebrook Hill mines, to , some gold-bearing), and which are described below. and flows. Further uplift and erosion in the Tertiary formed some minor In recognition of the recreational activity of fossicking, sedimentary basins (Late Cretaceous to Recent), several of the best of these areas have been declared intercalated with numerous basalt flows (some highly official Fossicking Areas under the Mineral Resources zeolitised). Development Act 1995. These areas are specially set aside for the use of fossickers (gem and mineral Mining history collectors), and will not be included in any exploration licence or mining lease application. The areas and On a world scale, mining is a relatively recent fossicking restrictions are described in a booklet phenomenon in Tasmania, excluding some minor (Fossicking Areas in Tasmania, compiled by C.A. Bacon working of flints, ochre and other minerals by and R. S. Bottrill, 1997) available from Mineral Aboriginal people. A little and ore were Resources Tasmania. worked by convicts in the early 1800s, but the discovery of gold in northeastern Tasmania in 1852, Conditions apply to the use of Fossicking Areas. inspired by the Victorian gold rush, was the first real Fossickers should avoid causing undue damage to the impetus for mineral exploration (Dickens, 1995). land, and should take only a ‘fair share’ of material.

Tasmanian Geological Survey Record 2001/08 4 40°

MINERALS & MUSEUMS TOUR TASMANIA

SCALE 0 20 40 60 80 100 km

Burnie

Hampshire Devonport

Waratah Launceston Heazlewood Moina

Cradle Mountain

Zeehan Trial Harbour Dundas Queenstown Strahan

Hobart 43°

Cygnet

Lune River

145° 148°

Figure 2

Tasmanian Geological Survey Record 2001/08 5 Mineral Locations

Moina quarry rutheniridosmine, , , gold, tetraferroplatinum and ferronickelplatinum (Ford, of topaz (to 40 mm), , quartz, 1981). Some associated sulphide and arsenide minerals and occur in veins and joints and include cherepanovite, erlichmanite, hollingworthite, argillised pockets in Ordovician , altered by iridarsenite, kashinite and (Peck and Keays, Devonian . Tin and tungsten have been mined 1990). extensively in the district, as well as gold, bismuth, silver, zinc, lead and other commodities. Important minerals

Middlesex Plains :Ca3(Fe,Cr)2(SiO4)3; fine grained veinlets, bright green to ; hydrous. Crystals of chabazite (to 15 mm) occur in vesicles in Tertiary basalt, with some analcime, phillipsite, , : (Ni,Fe); metallic white, rusty. and natrolite crystals. Dypingite:Mg5(CO3)4(OH)2.5H2O; pale blue to white, botryoidal crusts. Lord Brassey mine :Ni3S2; bronzy yellow patches in The Lord Brassey mine is a small but world famous serpentine. deposit situated near the former mining town of

Heazlewood (fig. 3). This former nickel mine is the : NiCO3.6H2O; pale blue coatings and very source of many rare minerals and is the type locality for attractive crystals, < 2mm. heazlewoodite and hellyerite (Andersen et al., in press). Molybdenite: MoS2; small patches of massive dark The discovery of the nickel mineralisation around grey to occasionally purple grey. Brassey Hill (Nickel Hill) was made in the 1890s when Reevesite:NiFe 3+(CO )(OH) .4H O; a lemon yellow prospectors were searching for ‘osmiridium’ 6 2 3 16 2 crust on serpentine. (-group minerals), of which the nearby Bald Hill locality was an important source. In 1896, an adit Retgersite: NiSO4.6H2O; pale to mid blue crusts. was driven into the hill by the Lord Brassey Nickel Company and a few tons of nickel sulphide ore was Theophrastite: Ni(OH)2; a green crystalline crust on extracted. slickensided serpentine. The nickel ore of the Lord Brassey mine, and the Unnamed: Ni-Fe sulphate; yellow-green, powdery. - ore of Bald Hill, occur within a large ‘’:Ni3(CO3)(OH)4.4H2O; the most obvious body of serpentine, part of a large Cambrian ultramafic nickel ‘mineral’; emerald green coatings and complex consisting originally of and mammillary, stalactitic or amorphous encrustations , altered mostly to green-black lizardite. along the shear planes and joint surfaces of the During the latest stage of Devonian metamorphism, serpentine. fault-controlled bodies of fibrous and waxy green serpentine (chrysotile and ) were formed due Other minerals to (Peck and Keays, 1990). The nickel mineralisation at Lord Brassey appears to be localised Native Elements: Unnamed Bi-Ni-Fe-Pt alloy, within such an antigorite-bearing body auricupride. and can probably be ascribed to this stage (Peck and Sulphides: covellite, , , pyrite, Keays, 1990). Other links to late -related, , , , . -like metasomatism include vein-style , , chlorite, andradite, , molybdenite and Silicates: antigorite, chrysotile, clinochlore, diopside, magnesite (Mann, 1988; Andersen et al., in press). , grossular, lizardite, , palygorskite, stevensite, talc. The nickel mineralisation is seen as small veins and pods of primary sulphides, principally heazlewoodite, Carbonates: , magnesite, otwayite, pyroaurite. which is intergrown with awaruite, magnetite, andradite, chlorite and other minor nickel, iron and Others: annabergite?, ?, , magnetite. copper sulphide minerals. Groundwater percolating up through shear planes within the serpentine has Mt Bischoff reacted with the primary sulphide minerals to form the The Mt Bischoff mine was discovered by part-time secondary nickel mineralisation (Henry and Birch, prospector James ‘Philosopher’ Smith in 1871, and for 1992). many years was one of the world’s richest tin mines The area was also worked extensively for alluvial (Groves et al., 1972). After 70 years of continuous ‘osmiridium’, containing various platinum group production, the Mt Bischoff mine closed in 1947. Since alloys, mostly osmium and iridium with minor then, mining ventures have only been spasmodic.

Tasmanian Geological Survey Record 2001/08 6 Hampshire 10 km Burnie u 2 u Devonport 1

Launceston

15 11 14 u Waratah Moina u u 3u Heazlewood u 12 u 4 uu6 16 5 u u u u u Savage River 17 13 9 8 u10

Cradle Mountain u 7 Zeehan

Figure 3 The Waratah district — sketch map and principal mineral deposits: 1. Kara W-Fe mine; 2. Hampshire Ag mine; 3. Stormont Bi-Au mine; 4. Shepherd and Murphy Sn-W-Bi-Au mine; 5. Moina quarry and All Nations Sn-W mine; 6. Sayers and Princess Sn-W-Be mines; 7. Mt Farrell Pb-Ag mine; 8. Gads Hill (zeolites); 9. Middlesex Plains (zeolites); 10. Que River and Hellyer Pb-Zn-Ag-Au mines; 11. Mt Bischoff Sn mine; 12. Magnet Ag-Pb-Zn mine; 13. Cleveland Sn mine; 14. Lord Brassey Ni mine; 15. Bald Hill Os-Ir mines; 16. Savage River Fe mines; 17. Heazlewood Ag-Pb mine.

Mt Bischoff was the first major mineral resource largely retrogressed. The highest tin grades were developed in Tasmania, with a total production of found within a quartz-pyrrhotite-topaz-fluorite around 62 000 tonnes of metallic tin. The discovery assemblage (the most strongly altered dolomite provided the impetus for exploration of other areas of replacement rocks) adjacent to the dykes (now largely the west coast and the subsequent discovery of other worked out). Dolomite-replacement mineralisation is mining areas such as Mt Lyell and Renison. found at the Greisen Face, where talc-pyrrhotite alteration occurs, and at the Slaughteryard Face, where Geology quartz-pyrrhotite alteration and fluorite ‘nodules’ Precambrian quartzite, shale and dolomite at Mt occur. Bischoff have been intruded by a radial group of Devonian quartz- dykes and Dyke mineralisation dykes, related to the nearby Meredith granite. Tin-base Greisenised dyke rocks are characterised by a white, metal sulphide mineralisation accompanies these fine-grained groundmass of quartz and topaz, with dykes, and occurs as a replacement of dolomite, as phenocrysts variably pseudomorphed by greisenised dykes, and as veins and linings siderite, pyrrhotite, quartz, topaz, pyrite, fluorite and (Groves et al., 1972; Wright and Kwak, 1988; Halley and cassiterite. One of the most prominent features of Mt Walshe, 1995; Sorrell, 1997; fig. 4). Tin mineralisation occurs within a radius of about one kilometre from the Bischoff is the Western Dyke, a greisenised porphyry summit of Mt Bischoff, and several silver-lead- with cassiterite both disseminated and coating joint deposits surround the mine. surfaces. zones were minor. Veins and fracture linings Dolomite-replacement mineralisation Fissure lodes are a late phase of mineralisation, Dolomite-replacement mineralogy is dominated by cross-cutting dykes and country rocks. They contain sulphides (mostly pyrrhotite), Fe-Mg-Mn carbonates, variable proportions of quartz, siderite, , fluorides (fluorite, ), and topaz, fluorite, cassiterite, wolframite and sulphide silicates (, , minerals (pyrite, pyrrhotite, , , , phlogopite, talc and serpentine), in part as , bismuthinite, As-Sb-Bi sulphosalts and magnesian skarns and ‘wrigglite’ (banded skarn), ).

Tasmanian Geological Survey Record 2001/08 7 SUMMIT NORTH FACE FACE

QUEEN DYKE

LITTLE WHEAL

BROWN FACE FACE

DYKE SLAUGHTERYARD FACE STANHOPE FACE

STANHOPE DYKE

WHITE Z GREISEN Y FACE FACE

GOSSAN PIG

FACE FLAT ACE DYKE

WHITE F

HAPPY VALLEY ALLEN’S FACE WORKINGS

X Quartz-feldspar porphry

Dolomite

0 50 100 150 SCALE Quartzite and shale

Black face of open cut workings

Figure 4 The Mt Bischoff mine (from Halley and Walshe, 1995)

Tasmanian Geological Survey Record 2001/08 8 Mineralogy transparent colourless crystals of fluorite, almost always as cubes, sometimes elongated or flattened, More than 100 mineral species have been recorded occurring on Fe-magnesite. Associated minerals from Mt Bischoff. The extensive alteration and large included quartz, pyrite and sphalerite. Green fluorite, amounts of magnesium and in the system sometimes with purple cores, has been found near the produced uncommon minerals such as sellaite, White Face dyke in recent years. Near the gossan face chondrodite, norbergite, wagnerite and dark purple fluorite occurs as complex (Wright and Kwak, 1988; Halley and Walshe, 1995; cubo-octahedral crystals with tourmaline, siderite, Sorrell, 1997). pyrite, marcasite and smoky quartz. Other fluoride minerals identified include sellaite, Pale to mid-blue, opaque crystals of beryl up to 50 mm prosopite, ralstonite and weberite. in length occur at Mt Bischoff, especially near the Slaughteryard Face, associated with an emerald green Quartz tourmaline. Some of these crystals exhibit colour Abundant small, white to colourless quartz crystals zoning which can be seen on the flat terminations of the occur in the porphyry dykes and in other areas such as hexagonal prisms. Other beryllium minerals recorded the Happy Valley Face, occasionally as wheatsheaf from Mt Bischoff include bavenite, hambergite and aggregates. Smoky quartz specimens to 40 mm are phenakite. much less common but very aesthetic, occurring with purple fluorite and siderite crystals. Carbonate minerals The major carbonate present is commonly referred to Sulphide minerals as siderite, but most appears to be an Fe-magnesite, Pyrite and pyrrhotite are ubiquitous. Pyrite can occur except in more quartz-rich rocks. Generally the lighter as attractive crystals, often as cubes or less commonly the colour of the specimen, the less iron content. pyritohedrons and other forms, although some does is rare here. Most siderite/magnesite is decompose. Other sulphides found in crystalline form found as tabular hexagonal crystals to 50 mm across include , marcasite and sphalerite. and is common in the dolomite replacement bodies, often associated with fluorite. Topaz Cassiterite The porphyries contain a compact fine-grained form of topaz known as pycnite, found as pseudomorphs after Cassiterite was the most important tin mineral mined feldspar, and as radiating groups of transparent at Mt Bischoff. It occurs in a number of environments acanthine crystals to 2 mm. Coarser crystals are rare. and was particularly abundant in the dolomite replacement bodies (especially the White and Brown Tourmalines faces). Much of the cassiterite mined was eluvial or alluvial, released through processes. In Tourmaline is common at Mt Bischoff, generally as 1880, a five hundredweight (250 kg) nugget was blue to green masses or thin tufted acicular crystals and recovered from the Slaughteryard Face. It is still rarely as very fine-grained botryoidal masses. possible to pick up masses of cassiterite up to 60 mm Compositions range between dravite, schörl, olenite with bright euhedral crystals in cavities. Bright and foitite. Elbaite has also been reported but not red-brown, yellowish or black crystals to 3 mm can be confirmed. found lining joints in the dyke rocks and sedimentary rocks adjacent to the dykes. Crystalline cassiterite Minerals Reported generally occurs as short, equant prisms, often Native elements: , bismuth, copper, gold, twinned, or rarely acicular crystals to about one graphite, sulphur. millimetre. Stannite and teallite are the other tin minerals recorded here. Sulphides: arsenopyrite, berthierite, bismuthinite, boulangerite, , chalcopyrite, galena, Fluorite jamesonite, marcasite, molybdenite, proustite, pyrargyrite, pyrite, pyrostilpnite, pyrrhotite, This is abundant in many parts of the mine, sphalerite, stannite, stibnite, teallite, . particularly the dolomite replacement bodies and veins, especially in the Slaughteryard Face. It is found Oxides: brucite, cassiterite, chromite, corundum, mostly as cubes to 30 mm, modified by octahedral (111) cuprite, diaspore, gahnite, , , and to a lesser extent, dodecahedral (110) faces on a magnetite, , , thorianite, tungstite. matrix of either magnesite or siderite. Most specimens Halides: bodalyrite?, fluorite, halite, prosopite, are transparent lustrous crystals, either colourless or ralstonite, sellaite, weberite, sylvite. pale blue, but massive purple fluorite also occurs. Some brown octahedral fluorite occurs in cellular Carbonates: , aragonite, , calcite, quartz-topaz-sellaite. Part of the Happy Valley Face dolomite, magnesite, , rhodochrosite, was worked in the late 1980s for specimen material; siderite, smithsonite.

Tasmanian Geological Survey Record 2001/08 9 Sulphates: barite, chalcanthite, copiapite, goslarite, Molybdenite: MoS2; hexagonal flakes. gypsum, halotrichite, jarosite, melanterite. : CaWO4; disseminated or rare white Silicates: , , , andradite, annite, bipyramidal crystals. , bavenite, beryl, , chondrodite, chrysotile, clinochlore, clinohumite, dravite, elbaite, Stolzite: PbWO4; rare, orange blocky to bladed enstatite, , foitite, , ?, crystals. hisingerite, , hydrogrossular, illite, : (tremolite-actinolite, hastingsite, , lepidolite, lizardite, microcline, ferroedenite, etc); fibrous green-white crystals. muscovite, natrolite, norbergite, olenite, opal, orthoclase, palygorskite, phlogopite, pyrophyllite, : (diopside-), green-black quartz , schorl, sillimanite, talc, , topaz, crystals. tourmaline, tremolite, vesuvianite, wollastonite, . Rarer and/or less obvious minerals and other: arsenobismite, , Skarn minerals: anorthite, ; vesuvianite; hambergite, isokite, monazite, scorodite, scheelite, wollastonite. vivianite, wagnerite, , wolframite Weathering zone: anthoinite and mpororoite (hydrous (ferberite), . Al-Fe tungstates, alteration products of scheelite), hematite, montmorillonite. Kara mine Granite minerals: allanite, biotite, chlorite, This is a relatively recent mine, having operated since fluorapatite, orthoclase, , quartz, sphene. 1977, initially as a scheelite mine but now producing mostly magnetite. There is potential for some other Sulphides: aikinite, arsenopyrite, bismuthinite, products, including wollastonite, and gold. chalcopyrite, galena, pyrite, sphalerite. There are a number of skarns in the Kara district, variously dominated by magnetite, garnet, Colebrook Hill, Dundas vesuvianite, wollastonite, pyroxenes, amphiboles and This location has produced Australia’s best other minerals (Kwak, 1987; Whitehead and Turner, ferroaxinite specimens, some of which are world class. 1990). These occur in Ordovician near the The deposit is hosted by an unusual skarn, sometimes contact with Devonian granite. The Kara described as a limurite or -hornfels, probably magnetite-scheelite bearing skarns occupy a derived from calcareous or dolomitic rocks associated trough-like pendant within a Late Devonian red with mafic-ultramafic intrusive rocks (Blissett, 1962). granite known as the Housetop Granite. Ore-grade The skarn has formed where boron and sulphur-rich scheelite and magnetite mineralisation at the Kara solutions from an underlying Devonian granite reacted No. 1 deposit are hosted by andradite-- with the reactive -rich types. The mine vesuvianite skarn which forms an irregularly-shaped was originally worked for copper, but various silver, blanket draped 15–25 m above the granite. Between the gold, tin, lead, zinc, tungsten and other minerals are skarn and the granite is a tungsten-poor, also present. The deposit is very complex and of great quartz-epidote reaction zone (Whitehead and Turner, mineralogical interest. Specimen minerals are usually 1990). The skarns are variably retrogressed to dissolved from the enclosing calcite with acids. The amphiboles ± epidote and fluorite and are mostly area is in a designated fossicking reserve, but is difficult overlain by Tertiary basalt. to access.

Major minerals Minerals that can be collected and identified

Andradite:Ca3Fe2(SiO4)3; large, lustrous, brown in hand specimens dodecahedral crystals. Calcite: CaCO3; very common as white to colourless massive material, and less commonly as Bavenite:Ca4 (Al,Be)4 Si9 O 26(OH)2 ; colourless radiating/bladed crystals. well-formed rhombohedral crystals.

Calcite: CaCO3; white rhombic to bladed crystals. Chalcopyrite: CuFeS2; common as massive or granular material with a bright brassy yellow colour and Danalite:Fe4Be3(SiO4)3S; coarse red tetrahedral rough fracture, sometimes tarnished purplish. crystals. : CaBSiO4(OH); uncommon, as glassy white or Epidote:Ca2FeAl2(SiO4)(Si2O7)(O,OH)2; small green very pale blue-green, short prismatic monoclinic prismatic crystals. crystals to about 20 millimetres.

Fluorite: CaF2; purple octahedral crystals. Ferroaxinite:Ca2(Fe,Mn)Al2BSi4O15OH; this is a dominant mineral in the lodes and occurs as massive Magnetite:FeO ; good, large dodecahedral crystals. 3 4 or crystalline material of a deep violet colour.

Malachite:Cu2(CO3)(OH)2; green, botryoidal. Well-formed wedge-shaped triclinic crystals up to Tasmanian Geological Survey Record 2001/08 10 20 mm in length occur, and may be very lustrous and Bindheimite:Pb2Sb2O6(O,OH); earthy, yellow, with attractive. crocoite; sometimes labelled massicot.

Arsenopyrite: FeAsS; this is rather abundant as : PbCO3; this area is famous for its ‘chrome massive material or as excellent orthorhombic cerussite’, which is locally abundant as very crystals to about 10 mm, with a bright silver-grey attractive crystalline aggregates of complex yellow colour. crystals, possibly coloured by small traces of . More normal white to colourless Quartz: SiO ; this is quite common as massive material 2 cerussite is also common at some mines. and as hexagonal crystals, milky white in colour, to

about 20 mm in length. -law twins occur. Chalcophanite: (Zn,Mn,Fe)Mn2O5.2H2O; this mineral occurs as finely drusy masses of lustrous purplish Tremolite-actinolite:Ca(Mg,Fe) Si O (OH,F) ; this 2 5 8 22 2 black hexagonal crystals on Mn oxides. occurs as a massive, coarse-grained fibrous material, and as radiating aggregates and ragged to fibrous Chlorargyrite: AgCl; this mineral forms waxy masses monoclinic crystals, up to 20 mm or so in size. The and crusts varying from yellow to green when fresh, colour is usually a pale grey-green. darkening to violet brown with exposure to light. It was an important silver ore in the gossans. Scheelite: CaWO4; this mineral has been reported rarely as small groups of white tetragonal crystals. Coronadite: PbMn8O16; this mineral is present in the gossans as massive or stalactitic, hard grey material. Other minerals reported from this locality Crocoite: PbCrO4; this mineral is very common here as Sulphides: loellingite?, pyrite, pyrrhotite, , attractive, fine, monoclinic prismatic to bipyramidal galena, sphalerite, marcasite, tetrahedrite, millerite. crystals to 50 mm, usually hollow, with a bright orange to red colour. The crystals occur as entangled Secondary minerals: azurite, malachite, copper, masses, as single crystals on gossan or , or cuprite, olivenite? (var. leucochalcite), ?, more rarely intergrown with or yellow connellite?, , rosasite, , ‘chrome cerussite’. Large terminated crystals occur chalcanthite, chrysocolla, , posnjakite, but are relatively uncommon. spangolite. Dundasite: PbAl (CO ) (OH) .H O; botryoidal- Other: boracite?, danburite, schorl. 2 3 2 4 2 fibrous aggregates of white to pale green crystals with crocoite. Serpentine Hill – Nevada Creek – Stichtite Hill, Dundas Gibbsite: AlO(OH); botryoidal to massive, white to yellow and black where impure; overgrows crocoite. This area is one of the principal sources of stichtite specimens in the world. It is hosted by sheared Goethite: FeO(OH); an important constituent of the Cambrian serpentine bodies. gossans. Usually massive, powdery yellow to brown and black when massive; pseudomorphs siderite. The stichtite replaces small disseminated chromite/ magnesiochromite grains, and is also remobilised into Grimaldiite: CrO(OH); a soft, grey to dark green coarser patches. It may be intermixed with its powdery mineral replacing chromite and coating polymorph , and may occur with crocoite. aragonite, chlorite and magnetite, hosted in serpentine. : CuPb(SO4)(OH)2; deep blue, prismatic crystals with cerussite and . Crocoite mines, Dundas :Pb5(AsO4)3Cl; relatively rare in the gossans These old Ag-Pb mines in western Tasmania include as small, colourless to yellow, orange, red and the Adelaide, Red Lead, Dundas Extended, West brownish-green hexagonal prismatic crystals. Comet, Platt, Kozminsky and Kapi mines (fig. 5), and Sometimes described as vanadinite. are the prime sources for crocoite in the world. Some of these mines are still being worked for specimen Muscovite: (‘fuchsite’) Massive, bright green clays are material. The primary ore occurs as Pb-Zn-Ag mostly this chromian . sulphides in veins in siderite–ankerite-rich fault zones Petterdite (new species): PbCr2(CO3)2(OH)4.H2O; pink cutting Cambrian serpentinite and ultrabasic-derived to lilac, very fine grained coatings on galena with , and Precambrian slate. The ore and host anglesite and cerussite. rocks in upper levels are largely altered to clays and gossan, but the crocoite may grow freely in vughs and Philipsbornite: PbAl3(AsO4)(AsO3OH)(OH)6; grey, joints. green, yellow to off-white; much was previously described as weilerite, gorceixite or . Minerals of Dundas Phosgenite:Pb2(CO3)Cl2; recorded in the gossans as Anglesite: PbSO4; occurs uncommonly as white to grey adamantine, brown to colourless crystals on galena. or green orthorhombic crystals to a few millimetres Rarely reported, but probably mistaken for anglesite with cerussite, usually coating galena. or cerussite.

Tasmanian Geological Survey Record 2001/08 11 u 17 Waratah u18 Rosebery Renison u 10 u 19 11 u u 8 u 15 u 9 Dundas 1 u 6 u u 5 2 uu Zeehan u 4 3 u u 7 13 u u 12 Remine 16

u Queenstown 14

5km

Strahan

Figure 5 Sketch map and principal mineral deposits, Zeehan district. 1: West Comet and Dundas Extended mines; 2: Adelaide mine; 3 Red Lead mine; 4: Stichtite Hill; 5: Platt and Kosminsky mines; 6: Comet-Maestries mines; 7: South Comet mine; 8: Kapi mine; 9: Nevada Creek; 10: Colebrook Hill; 11: Serpentine Hill (Tunnel Hill); 12: Sylvester/Queen mines; 13: Tenth Legion; 14: Trial Harbour Ni mines; 15: St Dizier Sn mine; 16: Comstock mine; 17: Rosebery mine; 18: Renison Sn mine; 19: Hercules mine.

Pyrolusite: MnO2; this powdery brown-black to Silicates: actinolite, epidote, halloysite, hornblende, silvery grey mineral occurs in the gossan. kaolinite, quartz, romanechite, serpentine, talc, wollastonite. :Pb5(PO4)3Cl; occurs in some mines as crusts of bright green prismatic crystals forming Others: atacamite, barite, , corkite, evansite, attractive combinations with crocoite. hinsdalite, langite, , . Unknown: Mn-Cr-Pb-O; black, platy, resembles chalcophanite. Trial Harbour nickel mine Other minerals reported in the Dundas district The nickel of this area are similar to those of the Native elements: gold, graphite, lead, silver, sulphur. Lord Brassey mine at Heazlewood. The mineralisation Sulphides: arsenopyrite, bismuthinite, is hosted by a body of serpentinised Cambrian boulangerite, chalcopyrite, cosalite, dufrenoysite, ultramafic rocks which have been metasomatised by , freibergite, glaucodot, galena, the nearby Devonian Heemskirk Granite. gudmundite, jamesonite, loellingite, marcasite, This deposit contains disseminated heazlewoodite, pyrite, pyrargyrite, proustite, sphalerite, stannite, chromite, magnetite and awaruite in serpentine with stephanite, tetrahedrite and zinkenite. minor millerite, bravoite, violarite, sphalerite, galena Oxides: arsenolite, bismite, bismutostibiconite, and shandite (Ni3Pb2S2) for which this is the type cassiterite, cervantite, chromite-magnesiochromite, location. Other minerals include zaratite, reevesite, cuprite, ferrotantalite, hematite, , aragonite, talc, hydromagnesite and tremolite. Nickel , lepidocrocite, litharge, lithiophorite, mineralisation at the related Avebury deposits, a few magnetite, minium, senarmontite, stibiconite, kilometres to the east, is presently being evaluated for -ranceite, valentinite. mining. The deposits comprise a number of small but Carbonates: ankerite, aragonite, azurite, calcite, Ni-rich bodies (more S-rich than Lord Brassey and Trial dolomite, hydrocerussite, malachite, rhodochrosite, Harbour), containing pentlandite, pyrrhotite, siderite, stichtite. chalcopyrite, magnetite, niccolite, pyrite and valleriite.

Tasmanian Geological Survey Record 2001/08 12 The Mt Lyell mines decades, particularly from the Prince Lyell mine, and contains pyrite, chalcopyrite, and minor This group of mines near Queenstown was at one stage , molybdenite, galena, sphalerite, bornite collectively one of the world’s largest copper with traces of other sulphide minerals. Gangue producers, and production has been almost continuous minerals, in approximate order of abundance, for nearly 120 years. They are some of the oldest include quartz, muscovite, chlorite, siderite, significant mines in Australia, and have produced magnetite, hematite, rutile, pyrophyllite, , about 1.4 Mt of copper, 43 t of gold and 733 t of silver barite, fluorite, calcite, ankerite, zircon and from some 119 Mt of ore (to 1999). The field was found monazite. in 1883, at the (which was first worked as a gold mine), and has been responsible for a large 0 Higher grade bornite-rich ores along the Great Lyell proportion of Tasmania’s gold production, as well as Fault. These appear to have been remobilised during most of its copper. Devonian syn-deformational, fault-related hydrothermal events, and are common in western The Mt Lyell mines are mineralogically most important Tasmania, often associated with Devonian granites as the co-type locality for the rare copper-iron-tin (Solomon et al., 1987). The bornite-rich sulphide , named after Sir Douglas mineralisation is characteristic of the North Lyell Mawson, the Antarctic explorer and geologist area but is somewhat variable in nature. Ore (Markham and Lawrence, 1965). Many other rare minerals include bornite, chalcopyrite, pyrite, minerals are also recorded from these mines, including chalcocite, tennantite, galena, betekhtinite, betechtinite, florenceite, svanbergite-woodhousite, mawsonite, digenite, sphalerite, molybdenite, , hessite, , magnesiofoitite, linnaeite, stromeyerite and others. Gangue minerals and stromeyerite. At least 85 species have been are as above, but cherty quartz, barite, fluorite and reported from the mines, many in attractive specimens. hematite are typically more abundant. The mineralisation is mostly hosted by schistose, highly altered rhyolitic to andesitic lavas and tuffs of 0 ‘Copper-clay’ deposits containing native copper, the Cambrian , with minor cuprite, chalcocite, digenite, bornite, covellite, occurrences in Ordovician and chalcopyrite, galena, sphalerite and goethite in limestone, and appears to be controlled by the illite-kaolinite clays derived from deeply weathered intersection of two major faults. Devonian argillaceous Ordovician limestone. The origin of bodies cut the ores, but appear unrelated these is unclear; they are possibly related to to mineralisation (Baillie and Sutherland, 1992). The Devonian hydrothermal activity, or Ordovician to mineralised zone covers some 10 km2 (fig. 6) and is up Recent weathering (Solomon et al., 1987). to about 800 m thick (Solomon et al., 1987). There are five major styles of mineralisation: Summary of Mt Lyell mineralogy (from Bottrill, Olubas and Adams, in prep.) 0 Massive pyrite-rich bodies, with colloform textures and high-grade copper, gold, arsenic and silver-rich Native : copper, gold, silver (Au, Hg-). shoots. These are postulated to have formed at or Halides: fluorite. near the Cambrian seafloor, as volcanogenic massive lead-zinc deposits (Solomon et al., 1987). Oxides: , cuprite, delafossite, goethite, High-grade ore shoots in the massive pyrite bodies hematite, magnetite, rutile, tenorite. were the original ores mined (after working of the Sulphides and sulphosalts: aikinite, arsenopyrite, gossan cap for gold), particularly in the Mt Lyell berzelianite, betekhtinite, bornite, bournonite, (Blow) and South Lyell mines. These shoots calaverite, chalcocite, chalcopyrite, clausthalite, contained pyrite, chalcopyrite, tetrahedrite, covellite, cubanite, digenite, djurleite, enargite, tennantite, stromeyerite, arsenopyrite, molybdenite, galena, geffroyite?, hessite, jalpaite, linnaeite, enargite and 2–3 g/t gold (Markham, 1963). Gangue mawsonite, molybdenite, pentlandite, petzite, minerals include quartz, barite, hematite, muscovite pyrite, pyrrhotite, renierite, sphalerite, stannoidite, and pyrophyllite. stromeyerite, tellurobismuthite, tennantite 0 Banded, thin pyrite lenses with chalcopyrite, galena tetrahedrite, wittichenite. and sphalerite (volumetrically very minor). These Phosphates: florenceite-(Ce), fluorapatite, gorceixite, are also postulated to be Cambrian volcanogenic monazite, svanbergite, vivianite, woodhousite. massive sulphide deposits (Solomon et al., 1987). The banded pyrite ores contain grades of up to 28% lead Silicates: albite, chamosite, clinochlore, clinozoisite- and 20% zinc. epidote, illite, kaolinite, magnesiofoitite (an alklai- deficient tourmaline), muscovite, pyrophyllite, 0 Disseminated, low to moderate-grade chalcopyrite quartz, topaz, zircon, zunyite. and pyrite. This is also considered to be Cambrian in Sulphates: , barite, boothite, chalcanthite. age, probably formed during early sub-seafloor alteration of the volcanic rocks and is highly Carbonates: ankerite, calcite, dolomite, malachite, deformed. It is the principal ore mined in recent siderite.

Tasmanian Geological Survey Record 2001/08 13 Figure 6 Mt Lyell mines (from Solomon, 1969).

Tasmanian Geological Survey Record 2001/08 14 The minerals of the Cygnet district Livingstone mine, the King Hill and Black Jack prospects (Taheri and Bottrill, 1999). This section has been adapted from Sorrell and Bottrill (1998). The following minerals have been reported (Sorrell and Bottrill, 1998). The Cygnet district has the distinction of being the site of some of the earliest mineralogical, geological and Primary minerals of the porphyries: aegirine, petrological investigations in Australia. Peron (1807) ?, albite, allanite, amphiboles (including reported on some rocks thrown at him by natives (they pargasite, ferropargasite, edenite, hastingsite, probably just wanted a mineral identification!) during reibeckite and magnesiohornblende), analcime, the sojourn with Nicolas Baudin in 1801, described by , andradite, anorthoclase, augite, biotite, von Buch. The mineralogist A. W. Humphrey arrived bytownite, cancrinite, corundum, diopside, in 1804 with some early settlers and scientists and also fluorapatite, eudyalite, haüyne, hedenbergite, collected and described rocks from the area (Ford, ilmenite, labradorite, magnetite, , nosean? 1983). Twelvetrees and Petterd (1899) conducted some , orthoclase, pyrochlore?, quartz, sanidine, of the earliest petrographic investigations in Australia sodalite, , sphene, wöhlerite? on some rocks from Cygnet. Secondary minerals of the porphyries: aragonite, The geology at Cygnet is dominated by glaciogene barite, calcite, epidote, marialite, mordenite, Permo-Carboniferous and siltstone, natrolite, pectolite, scolecite, stellerite. intruded by Jurassic dolerite and numerous Minerals mostly of the contact rocks and : Cretaceous alkaline igneous intrusive rocks. The latter andalusite, chlorites, graphite, muscovite, rocks, a variable group of quartz-poor porphyritic phlogopite, pigeonite, prehnite, pyrrhotite, rutile, rocks usually described as sanidine, monzonite or tremolite-actinolite-ferroactinolite, wollastonite, syenite porphyries, comprise the Cygnet alkaline zircon. intrusive complex, and were formed in response to the rifting of Tasmania from Antarctica about 100 million Minerals mostly of the mineralised zones: years ago. They are the most interesting rocks in the arsenopyrite, cerussite, chalcopyrite, cinnabar, area mineralogically, containing most of the ~80–90 covellite, galena, goethite, gold, gypsum, hematite, species recorded from the area. They are dominated by jarosite, marcasite, zincian montmorillonite- sanidine and plagioclase, with minor pyroxenes, nontronite, opal, plumbogummite, pyrite, amphiboles, and many other minerals. They pyromorphite?, siderite, silver minerals are also associated with gold mineralisation at several (chlorargyrite?), sphalerite, sulphur. areas, particularly the Mt Mary gold mine, the

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