The Puttapa Zinc Mine in Australia

The Puttapa Zinc Mine – South Australia

A relatively unknown and obscure zinc deposit in the remote area of the Australian Outback has become famous for producing dramatic fluorescent specimens of willemite mixed with several other minerals. These pieces exhibit bright fluorescence, most with 4+ colors, extreme phosphorescence, and wild patterns of color. Introduced to the market in limited quantities (as of the date of this writing – Oct., 2011) they have been a big hit. The Puttapa deposit was first mined in 1974. It has also operated as the EZ Mine, the Beltana/Aroona Deposit, or just the Beltana Mine. Puttapa is an open-pit mine, located just north of a small coalmining town called Leigh Creek (pop. 549) and about 1,300 kilometers west of Sydney. The ore from this high-grade zinc silicate deposit was directly shipped to smelters. As of 2007, the total resource was estimated to be 972,000 tons of ore. Mining operations ceased in January 2008. The mine property is owned by Pasminco/Perilya.

Zinc and lead-mineralized rock is found throughout the Adelaide Geosyncline (a sedimentary basin formed in Proterozoic/Cambrian time). The Puttapa Deposit, one of the highest-grade zinc deposits in the world, is situated in the northwestern part of this area, in the highly fossilferous Wilkiwillina Limestone. The principal ore mineral is willemite, surrounded by an intense hematite-dolomite alteration halo. Other major ore minerals found in the Beltana/Aroona/Puttapa deposits include smithsonite, coronadite, hedyphane, and mimetite. The major gangue minerals are manganocalcite, dolomite and quartz. Willemite ore occurs as a white “cement”, lining large cavities in a reddish clay/siltstone argillic matrix, as laminates embedded in this reddish siltstone, radiating clusters, zebra textures and as a direct replacement of fossils and algae layers (often referred to as “radiating willemite”). Arsenic and lead are mostly found in hedyphane, occurring as a greenish, coarse-grained replacement of cavity fillings and as white hexagonal crystals (up to 1 cm) in cavities. Lead minerals in fractures and as void fillings seem to crosscut willemite. Calcite and dolomite also crystallized in these cavities, along with hedyphane which is sometimes overgrown by calcite in the vugs. Coronadite (a manganese mineral) occurs in veins and is the main Pb mineral in the matrix. (“Formation of Willemite in Hydrothermal Environments”, Joel Brugger et all)

MinDat presently lists 36 mineral species from this locality while another list as many as fifty-two (but the larger number is a result of listing Adamite, Cuprian Adamite, etc. These duplicate entries are not included). Combining the two lists results in 58 different species. Little has been done to describe or identify the fluorescent minerals from the deposits.

Listed below are all the minerals noted as found in the Puttapa/Beltana deposits. This list is compiled from MinDat and an article on “fossicking” at Puttapa (“Fossicking for minerals at the Puttapa Zinc Mine, South Australia” - by Patrick C. Murphy & James N. Murphy)

Mineral List *reported to be fluorescent **fluorescent according to Mineralien Atlas c=common at Puttapa r=rare at Puttapa (These notations mostly based on “Fossicking” article)

 Fluorescence

Very little professional work has been done to identify the wild fluorescent colors found in specimens from Puttapa and the surrounding mines. Much of the identification is guesswork by the writer and some knowledgeable friends. We hope that the professionals in our hobby will become fascinated with these new rocks and help figure out what they are as they did in the early days of Greenland collecting.

Willemite seems to be usually fluorescent green but we have also seen a bluish/white fluorescence which may also be willemite (under MW both the green areas and the blue/white areas fluoresce a yellow color). So far, willemite is usually very phosphorescent

Aragonite reportedly is fluorescent blue/white in these pieces, but hedyphane is also reported to fluoresce that color. Calcite fluoresces a bright reddish/orange and might also fluoresce a dark purple.

Very often there are two colors of phosphorescence – blue and green. The green is likely willemite, while the blue could be aragonite?

Other minerals from the deposit not yet identified to be fluorescent, but are known to be fluorescent from other localities include: adamite, barite, dolomite, hyalite, tilasite, sphalerite and probably several more.

General Notes of Fluorescence

The “Fossicking for Minerals” article describes each mineral species in detail. In some cases, comments are made about fluorescence (or, just as significantly in other cases, no comments are made).

• Adamite – noted as being relatively common on matrix of willemite. Mg rich – but not noted to be fluorescent
• Aragonite – white acicular crystals reported, matted aggregates of “fibrous” crystals. “Some … is known to fluoresce green under SW”
• Calcite – reportedly widespread, but not common. No reference to the fluorescence
•  Hydrozincite – reproted to be very rare at Puttapa, but distinguished by its blu/wht fluorescence
• Smithsonite – very common, contains Mg but no reports of fluorescence
•  Willemite – “The mineral – even in its relatively pure massive white form … - does not fluoresce”. This statement seems untrue as willemite in all our specimens is wildly fluorescent

Generally we find the article lacking in observations are made about fluorescence.

Description of a cross section of the Puttapa Deposit from Datametallogenica

“Three irregular bodies of aphanitic, brecciated, hematite-pigmented willemite with bands, veinlets, breccias cement of white metacollofrom willemite and calcite, replacing and infilling tectonic blocks of dolomitized Ajax Limestone; breccias-cementing and fracture-coating later stage Pb-Zn arsenates (hedyphane, mimetite, etc.) and Mn hydro-oxides with Pb (coronadite).”

Locality Pictures

Graham Fraser - Collecting on one of the rockpiles found at Puttapa

Graham travels to the Puttapa Mine to collect these fabulous minerals. To date he has made four visits to the area and has collected some world-class specimens. He has not been granted permission to enter the old mine area as it is falling apart rapidly. However, the roads lined with waste rock, are quite rich in specimens.

Campsite

The area is quite dry and there are no public facilities nearby. Camp is setup near the best trees that can act as a windbreak and provide a little shade.

Select Specimen Photos