Electrifying Mining in NZ: It's Worth Its Weight in Gold
New Zealand has begun electrifying its mining industry, showing a sustainable way for the world to obtain the materials we need to transition to clean energy.
Gold and coal play a big role in the history of New Zealand—and both will probably continue to play a big role in the future of our planet. The lessons of the historic gold rushes and coal fields of New Zealand echo the experiences of mining communities across North America, with periods of booms and busts leaving a legacy of environmental degradation. Now, with its strong commitment to environmental protection, the little island country is showing the world how we can use modern technology to obtain gold, coal, and other critical materials in ways that can save our planet—for example, by using the “biggest EV in the country” to dig ore.
In 1842, whalers found gold on the North Island in the Coromandel Peninsula and a survey party found gold on the South Island near Nelson. But it wasn’t until 1852 that the first of a series of gold rushes kicked off, which eventually drew tens of thousands of hopeful immigrants to Aotearoa. In many places, such as Dunedin (which briefly became the most prosperous city in New Zealand), coal mines followed the gold mines to provide heat and power for growing populations and industry. Today, mining is the country’s most productive industry in terms of “gross domestic product per job filled.” Besides coal and gold, New Zealand has extensive mineral resources and petroleum reserves, giving it an opportunity to choose whether to make a fast transition to an economy fully powered by clean energy or turn back to fossil fuel.
Signs around the Coromandel peninsula, where I’m visiting now, advocate “mine e-waste, not Coromandel.” There’s certainly plenty of gold in discarded cell phones and computers (one study showed that the concentration of gold in e-waste is ten times higher than in raw ore), but even if we fully recycle all the metal we’ve ever mined, we’ll still need more.
In this week’s dispatch from New Zealand, I thought I’d take you on a quick tour of an active gold claim near Hokitika on the west coast of the South Island. This two-person operation hasn’t made the switch to electric equipment yet, but it’s not hard to imagine that one day they will, following the example of Oceana Gold Macraes Gold Mine, which announced on April 16, 2024, that they were ready to plug in and put a $10 million, 360-ton fully electric excavator to work 24/7.
The picture above is the first sign of an alluvial gold mining operation. This one was working old tailings in February 2024 on Maori land near Hokitika. In the 1800s, gold miners dug through river beds by hand, seeking nuggets, flakes, and grains of gold that settled to the bottom. Today, individuals and small companies can buy rights to rework these areas using modern, diesel-powered technology. At an active site, you’ll likely hear the sound of a pump running to provide a steady flow of water to separate gold from sediment.
The water used to separate gold from rocks and gravel travels in a loop from a holding pond up to the mining area and back down to the pond.
Alluvial deposits of gold require much less expensive equipment to mine than the quartz hard rock veins of gold in the Coromandel region. In hard rock mines, explosives blast apart solid rock, and then batteries crush those rock fragments to dust. In areas where gold can be found along river bottoms, the hard work of separating gold from surrounding rock has already been done over millennia by wind, rain, snow, and hail. Glaciers and rivers have naturally weathered and ground down mountains, sending sediment containing gold dust downhill toward the sea.
What took people months to do by hand and horse in the 1800s can be done in hours using excavators and sluices. The photo above shows how an excavator scoops up rocks and gravel then dumps them into a hopper above a rotating screen drum where water washes over the tumbling mixture and sends sediment down sluices on either side of the drum. Large rocks roll down the middle of the drum, while smaller material falls through the holes in the drum and cascades down the sluices.
In these close up pictures of the sluices, you can see how the sluices trap pebbles, sand, clay, and gold.
What you can’t see is the carpet fibers at the bottom of the sluice, where gold particles sink and nestle, being denser than other rocks.
In this area, the layer of sediment containing gold that has washed down from the mountains rests on an older layer of gray clay. That’s a convenient way to know how deep to dig. The original forest was removed in the 1860s, and the top layer of rock and soil was panned by hand. The high price of gold makes it economical to dig this area up once again to get the grains that the original prospectors missed.
The landscape will change once again; unlike the native forest that was allowed to regrow naturally on-site, non-native Monterey pine (Pinus radiata) must be planted once this century’s miners are done. The landowners would like to grow a plantation forest that can be harvested for lumber in 25 years or so.
The two brothers who were doing the mining have been using pretty much the same techniques and the same equipment for decades. Having just recently paid off the loans on the last of their fuel-burning equipment, they were skeptical that electric equipment would be practical—and certainly not economical. Their trail of gold leads along ancient riverbeds deep in the bush, far from power lines where they could plug in electric equipment. Batteries will need to become much better before they can imagine operating without burning fuel.
Ironically, it is the bigger mines with equipment that seems like it would be harder to electrify that are actually electrifying quickly. These big mines already have power plants on site, or they are connected to the power grid for lights, computers, and other electrical needs. They can begin using electrical equipment that can remain plugged in. Just like it was possible to buy a plug-in electric lawn mower long before battery-powered mowers became available, it’s possible to buy enormous plug-in mining equipment before battery-powered equipment of that scale is available. But given how quickly battery technology is improving, I’m guessing a lot of small-scale miners in New Zealand and all over the world will be electrifying much sooner than they expected.
Dispatches from New Zealand
Every other week, we share a dispatch from New Zealand showcasing interesting sustainable practices that differ from those in North America. In the alternate week, we continue to publish our series of practical action guides.
Last year, we explored the pathway to sustainable movement, energy, and goods. For the next few weeks, we’re exploring the pathway to sustainable food. From the standard American diet to a healthier plant-centered diet and from industrial farming to regenerative agriculture, stay with us on the journey to sustainability.
References and Further Reading
Gold Discoveries, An Encyclopedia of New Zealand
Dunedin, New Zealand History
Mining is New Zealand’s most productive industry, OceanaGold
Mineral resources potential, New Zealand Petroleum & Minerals
New Zealand's petroleum basins, New Zealand Petroleum & Minerals
Current trends in gold recovery from electronic wastes, Resource Recovery from Wastes
Mining is necessary for the green transition. Here’s why experts say we need to do it better, PBS News Hour
OceanaGold believes new electric excavator key to decarbonisation, RNZ
Mining Gold: Finding Better Ways, General Kinematics