Broken Hill: Australia’s silver city
Tony Forsyth (Australia)
Located over 1,100km west of Sydney in New South Wales, Australia is the city of Broken Hill (Fig. 1). Nicknamed Australia’s “silver city”, with a population of over 20,000 people, it is now a prosperous centre for mining, the arts, tourism and film production. However, my wife and I were here for other attractions of the city – its wonderful mineral specimens and the area’s links with Australia’s prehistoric past.
The stark country surrounding the town is semi-desert, part of the Australian outback. It usually receives less than six inches of rain in a year, but we were lucky – 2009/2010 was one of the wettest seasons in a generation. The reds, oranges and drab olive stretching to the horizon in every direction were now tinged with green.
Dominating the town is a high, flat-topped ridge, from which tumble scree slopes and abandoned slag heaps – detritus from the mining and all that remains of the original “Broken” hill. It is now known as the “line of lode” and the ridge was the site of the original mineral discovery by Charles Rasp, a boundary rider from Mount Gipps Station in 1883. Rasp collected what he thought were specimens of a black tin ore from the desolate and isolated ridge top. In September of that year, Rasp had the samples analysed and, instead of tin, found them to be rich in silver and lead.
Claims were quickly pegged across the top of the ridge and a syndicate formed to mine the deposit. By 1885, Broken Hill was Australia’s richest mineral field and, by 1890, a one-fourteenth share in the first syndicate was worth £1,250,000, a very large sum in the late 1800s. In 1885, one of many mining companies operating on the hill was the Broken Hill Proprietary Company Limited (BHP). This firm would eventually morph into the world’s largest mining company, BHP Billiton, made rich by what has since proved to be the world’s largest silver/lead/zinc body of ore (Fig. 3).
The ore was a bonanza for many of those early companies, who extracted thousands of ounces of silver to the ton in many cases. Large slugs of native silver and beautifully crystallised ores of silver, lead and copper were soon encountered. The earliest mines on the hill were just open cuts, with miners easily able to barrow and tunnel for the ore, using only a pick and shovel. However, soon the easily won ore from the hilltop was exhausted and the first of many shafts sunk deep into the ridge now appeared. Mining continues to this day, with a number of shafts now extending over 1,000m underground.
The ores contain an unusually rich concoction of elements. In turn, these spawn an equally rich array of rare and beautiful minerals. Over 300 discrete mineral species have been identified from the lode, with at least nine of these being ‘type’ species (that is, those mineral species new to science, which are first described from a deposit). One type species – raspite – immortalises the original discoverer of Broken Hill. In the late 1800s, the vughs(cavities in a lode) lined with glittering azurite (Fig. 4), cerussite (Figs. 5 to 7), anglesite, smithsonite and pyromorphite were drawing collectors and museum agents from all over the world, hoping to enhance their collections.
Especially notable were the superb specimens of reticulated and twinned cerussites.
A fabulous 30cm example in the collection of the Australian Museum in Sydney has been judged as the finest example of cerussite in existence. However, specimens of this calibre are unlikely to be encountered again, as the oxidised zone, which produced these beautiful specimens, was soon exhausted, as the mines gradually worked deeper into the hill.
My wife and I were keen to view some of these wonderful specimens and, if possible, to collect some minerals for ourselves. As temperatures can regularly exceed 40oC in summer, field collecting is only feasible in the cooler or winter months. We arrived in Broken Hill in early June to fine sunny days and frosty mornings (with little or no humidity, the temperature drops very quickly once the sun sets).
The “line of lode” mines are themselves are out of bounds to collectors, because of safety and security issues, but many of the smaller, abandoned outlying mines (Fig. 8) still provide amateur collectors with excellent specimens. If you are a mineral collector, then you know that you must be in the right place when all the main streets of a city are named “Oxide”, “Sulphide”, “Beryl”, “Crystal”, “Argent” and so on.
Broken Hill also has a keen mineral collecting club and, aided by the use of the Internet before our visit, we arranged to meet up with a group of local collectors. Equipped with “mud” maps of local mines and guidance to likely mineral collecting localities, we set out to see what we could find.
Drive any direction out of Broken Hill and one of the more noticeable features is the rocky outcrops that break the horizon. They glisten with flecks of mica, crystalline quartz and feldspar in the sunshine. Many of these pegmatites also contain deposits of staurolite, garnet, tourmaline and beryl (Fig. 9). Although not generally of gem quality, they are still valued for their fine crystal forms and associations. Just to observe and collect large crystals of garnet and beryl in situ is a great collecting experience.
Ten kilometres out of town, we walked over a ridge top which, for over 200m, was almost entirely composed of the black tourmaline variety schorl (Fig. 10), in jackstraw crystals in schist. Although small (10mm to 30mm), the lustrous, terminated prisms looked impressive when dozens of them were scattered across the rock faces. (The term ‘termination’ is commonly used in mineral terms to define a crystal that ends or finishes in a crystal face – or faces – rather than a broken or cleaved surface.)
The next day we fossicked (the Aussie word for gem and mineral collecting) for beryl crystals alongside a gravel road, southwest of the city. Before World War II, a large deposit of felspar that included crystals of beryl (that is (Be3Al2(SiO3)6, which is a rich source of the metal beryllium) was discovered. Later, during the Cold War, almost all the beryl output from the mine was diverted to the US nuclear power and weapons programme where beryllium was used as a moderator in nuclear reactions.
Although the mine is now off-limits, luckily for us, many of the spoil heaps have now been used as road fill. We were able to find several crystals of beryl, up to 100mm in length, encased in blocks of quartz and feldspar, which littered the roadside. The crystals were a creamy-yellow colour and mostly opaque, but all exhibited the typical beryl hexagonal prism faces and a few showed a termination.
The following day, we returned to Thackaringa to collect specimens of almandine garnet. A weathered pegmatite deposit had spawned loose crystals, which had tumbled down a hillside and gully. Most were quite weathered, but occasional crystals showed a distinctive ruby-red tinge and sharp, lustrous faces. Most crystals were 10mm to 30mm in size, but a deposit close by is currently being worked commercially by a specimen collector, who is producing sharp, opaque crystals that are over 100mm in diameter.
Taking a break from fossicking, we spent a day exploring the town. Our first stop was to visit the private collection of Milton Lavers. Milton’s collection is exceptional, not only for the extremely high quality of its pieces, but also for the fact that the collection (of many hundreds of specimens) is made up entirely of Broken Hill and district minerals. Another fine mineral collection is on view at the Albert Kersten Mining and Minerals Museum (locally referred to as the “Geocentre”) in the centre of town.
The Geocentre also has good displays on the history and complex geology of the area. A two-minute drive from the centre takes you to the top of the line of lode, providing a great view of the city, mines and surrounding desert. Also overlooking the town is the Miners Memorial (Fig. 14), commemorating those men (and children) who have perished in the mines over the past 120 years. The list of more than 700 names, which also include the year and cause of death, makes sobering reading.
We spent one more day fossicking for crystals of amethyst and smoky quartz at Corona Station, north of the city, before heading south to discover more about the pre-history of this interesting area.
Lake Mungo (Fig. 15) lies about 250km southeast of Broken Hill and is reached by gravel roads recommended for 4WDs only. It is not, as its name suggests, an actual lake, but a dry lake bed covered by saltbush and spinifex grass, and surrounded by a landscape of sand dunes and eroded gullies. The Willandra Lakes system, of which Mungo is but one, hasn’t held permanent water for over 17,000 years.
As far back as 60 to 70,000 years ago, the climate was far wetter and the lake and its surrounds was able to support a large and diverse range of wildlife. Extinct megafauna included large species of kangaroo and Diprotodon (a cow-sized grazing marsupial). Also attracted to this area by the permanent fresh water and an abundant food supply was a large population of early aboriginal people (Fig. 16). In 1969 and 1974, two skeletons (later nicknamed “Mungo Man” and “Mungo Woman”) were discovered, which put Lake Mungo on the palaeontological map. Scientists have identified these skeletons as the oldest anatomically modern human remains yet found in Australia. The oldest skeleton is at least 40,000 years old and also showed signs of a ritual cremation.
The area is now included within a national park and a well-equipped visitors centre explains a great deal of the past history and geology of the area. We set up camp not far from the centre to explore the area in more detail the next day. A self-guided tour takes visitors across the dry lake bed to an area called the “Walls of China”. Tour operators conduct day tours from both Broken Hill and Mildura in Northern Victoria to this location.
A car park is situated at the edge of the lake bed. From there, visitors are free to wander around a huge expanse of dunes, gullies and saltpans. It was within this area that the Mungo skeletons were discovered. Thousands of years of prevailing winds have heaped layers of sand and silt into a high, crescent-shaped ridge on the edge of the lake bed. Within these eroding layers can be seen the remains of the creatures that once lived on the shores of the lake. White fragments of bone spill down slopes or protrude from escarpments.
And the traces of the earliest Australians are everywhere. Ancient blackened hearths, with layers of ash and shellfish remains, can be seen sandwiched between layers of sand and silt. Prehistoric tools litter the landscape, once your eye is accustomed to spotting them. Small shards of flint and quartzite, and cores of chert lie scattered on the ground, just as their makers left them many thousands of years ago. To me, this was the highlight of our trip – to see these ancient relics and imagine the persons who created them and the immense time that has passed, and the environmental changes that have occurred, since their creation.
Tempted as you may be, all material at Mungo is protected and large fines apply for disturbing or removing any aboriginal material. Lake Mungo is a national park and was declared a World Heritage site in 1981.
Although Broken Hill and Lake Mungo are a little off the beaten tourist path, if you are visiting Australia and interested in minerals and prehistory, then these areas are well worth the effort of getting there. For more information, see: