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Dundas Extended Mine, Dundas mineral field, Zeehan district, Tasmania, Australia
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Latitude: 41°52'40"S
Longitude: 145°25'7"E
 
 
(NOTE: NOT the same mine as the Red Lead mine!)
The present Dundas Extended mine, about 1.5 km east of Dundas (not to be confused with operations of the same name conducted around 1900 in what is now the Red Lead mine lease) is presently worked for specimen material. It was probably originally part of the Central Dundas mine, adjacent to and west of the West Comet mine (see below). It has been worked intermittently by Mike and Eleanor Phelan since about 1985 (Fig. 16). The present operations are based on an old adit (Fig. 17) driven to intersect the West Comet Fault. Originally, the adit continued past the fault for some distance (now partly inaccessible) and although mineralisation was intersected no stoping was carried out. Recent operations have concentrated on the fault with minor workings developed at a depth of 50 to 60 m below the surface.
The NNE-trending West Comet Fault separates folded Cambrian Dundas Group sediments comprising siltstones and shales of mid-Cambrian age, and early Cambrian serpentinite. Fault breccia, consisting of crushed fragments of metasediments, is developed with increasing intensity towards the footwall. It includes a talc zone similar to that at the Razorback tin mine along the same fault zone to the north. Primary mineralisation consisting mainly of galena is most intense at the boundary, forming discontinuous pods, masses and stringers accompanied by intense silicification, with talc and porous to massive saccharoidal quartz development. Subsequent movement has shattered the primary quartzose rocks, forming a matrix for some of the secondary lead mineralisation. It is noted that, throughout the fault-hosted workings, small masses of incompletely decomposed galena are frequently encountered.
Anglesite is frequently the first alteration product of galena in the oxidised zone, but is present in only small amounts and is mostly fine-grained, white to pale grey and massive. From place to place, minor amounts of malachite, azurite and chrysocolla have been observed as facings and minute veinlets in the ore breccia. Crocoite and cerussite are the only mineralogically significant species in the mine. Delicate, reticulated masses of cerussite have been recovered from several sections of the present workings, especially near the top of the No. 2 raise and the south-east crosscut to it (Fig. 17). Associated with the normal white cerussite in this material are masses of so-called “chrome” cerussite of a pale to deep yellow or greenish yellow hue (Melchiorre et al., this issue). Sometimes these take the form of bevelled twinned "cogwheels" (Fig. 18), reminiscent of specimens recovered from the Magnet mine (Haupt et al., 1995). Beautiful aggregates of yellow plates have been found in the same environment (Fig. 19).
Crocoite from the Dundas Extended has perhaps not achieved the renown of that from either the Red Lead or Adelaide deposits. However, handsome specimens of acicular crystals on manganese oxide-stained or ferruginous gossan, quartz breccia and decomposed serpentinite have been recovered throughout the workings (Fig. 20). Doubly-terminated, elongated prisms to 20 mm were found in the No.1 raise (Fig. 21). Of particular interest is crocoite on shattered quartz breccia exposed in the upper workings. Here, aside from acicular crystals and elongated prisms, coatings of isolated crocoite crystals to 5 mm possessing a distinctly flesh-pink tint are found (Fig. 22). These “pseudo-bipyramids” display the forms {310}, {111}, {011}, and {012}, among others, and are quite unlike other material from the Dundas field. Analyses of the crystals indicate that they are, however, pure lead(II) chromate, with no hint of sulfate substitution in the lattice (Crane et al., 2001). Some good prismatic crystals have surfaced recently, resembling some Adelaide or Red Lead crocoite. The Dundas Extended specimens are characteristically associated with a whitish, granular quartz-rich matrix (sometimes including small quartz crystals).

Mineral List

Anglesite
Cerussite
Cerussite
var: Chrome-Cerussite

Crocoite
Galena
Quartz


6 entries listed. 5 valid minerals.

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References

Bottrill, R.S., Williams, P., Dohnt, S., Sorrell, S. and Kemp, N.R. (2006). Crocoite and associated minerals from Dundas and other locations in Tasmania. Australian Journal of Mineralogy. 12, 59-90

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