The 1.7-Billion-Year-Old Pipes That Leached a Continent's Copper

In the arid plains west of Lake Torrens, the ground is stained turquoise and malachite green. The colour comes from copper oxides that have bled out of the rock for more than a billion years. Here, at Mount Gunson, the earth is a wound that has never fully healed.

The Pipes That Rose From Magma

Mount Gunson sits above the Stuart Shelf, a Proterozoic basin that overlies the Gawler Craton. Around 1.7 billion years ago, volcanic activity beneath the basin drove superheated fluids upward through fractures in the sedimentary layers. These fluids, rich in copper and sulfur, rose through what geologists call "pipes"—vertical conduits that cut through the host rock like chimneys.

As the hydrothermal solutions cooled, they deposited chalcopyrite, bornite, and chalcocite—copper sulphide minerals that filled cavities and replaced the surrounding sediments. The pipes themselves are modest in size, rarely more than a few metres across, but they are densely mineralised. Over 1.7 billion years of erosion has stripped away the upper layers, exposing the tops of these pipes at the surface. The green and blue stains are the oxidised caps of a much deeper system.

The volcanism that drove this system was not explosive. It was the slow, steady heat of a cooling magma chamber beneath an ancient rift. The same heat that deposited the copper also cooked the surrounding sandstones into quartzite, hardening them against the erosion that would eventually expose the ore.

A billion and a half years after the fluids cooled, people would come looking for the green stains.

The Miners Who Came Before

The copper at Mount Gunson was not discovered by geologists. The Kokatha people, who have lived on these plains for tens of thousands of years, knew the green rocks well. They collected malachite and azurite for pigment and traded the copper-bearing stones across the desert. At a site called Cattle Grid, archaeologists have found stone hammers, grinding stones, and charcoal from fires used to heat and fracture copper-rich boulders.

Radiocarbon dates place this mining activity at around 500 CE—1,500 years ago. That makes Mount Gunson one of the oldest known copper mining sites in Australia, and one of the few places on Earth where Indigenous people extracted metal ore before European contact. The mining was selective: they targeted the oxidised caps of the pipes, where the copper was soft enough to hammer and grind.

There is no evidence they smelted the metal. They worked the ore cold, reducing it to powder for pigment and perhaps for trade. The green dust travelled. Kokatha trade routes carried it hundreds of kilometres, linking the Stuart Shelf to the Flinders Ranges and beyond.

The Modern Dig

European miners arrived at Mount Gunson in the 1860s, drawn by the same green stains. They dug shallow pits and shafts into the pipes, following the copper down. The ores were rich—some pipes yielded grades above 30 per cent copper—but the deposits were small and scattered. The mines closed and reopened in cycles, never quite paying.

In the 1970s, open-cut mining stripped away the weathered caps to reach the primary sulphides below. The operation was brief but productive: 1.5 million tonnes of ore at 2.5 per cent copper. Then the pit flooded, and the pumps were switched off.

Today, the site is quiet. The pit lake is alkaline and bright blue, coloured by dissolved copper. The old shafts are fenced off. The green stains on the outcrops are still visible from the road.

What the Pipes Remember

The Mount Gunson pipes are a reminder that mineral deposits are not simply geological curiosities. They are points of convergence between deep time and human time. The copper that rose through those pipes 1.7 billion years ago was not destined to stay buried. The slow work of erosion, the chemistry of oxidation, and the colour of the resulting minerals all conspired to make it visible. And once visible, it was inevitable that someone would pick it up.

The same pipes that fed a Proterozoic hydrothermal system also fed an Indigenous pigment trade and a colonial mining rush. The geology did not change. Only the hands that worked it.