Mining

• 1. Introduction

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  Mining pulled 8.5 billion metric tons of coal out of the Earth's crust in a single year, 2023. That is one number among many that show how deeply human life depends on materials buried in rock. Mining is the extraction of geological materials and minerals from the surface of the Earth. It supplies almost everything that cannot be grown by agriculture or built in a laboratory. The list of what comes out of the ground runs long: metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. For something to count as ore, it must be a rock or mineral that holds a valuable constituent, can be extracted, and can be sold for profit. How far back does this work reach in time? How does a company decide whether a buried deposit is worth digging for? And why has an industry so essential to daily life become tangled in disputes over poisoned rivers, collapsed tunnels, and the children sent down into them?

• 2. Roots In Ochre And Flint

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  About 41,000 to 43,000 years ago, Paleolithic humans dug into the ground at the Ngwenya Mine in Eswatini, the place radiocarbon dating marks as the oldest known mine in the archaeological record. They were after hematite, which they ground into the red pigment ochre. Mines of a similar age in Hungary may be sites where Neanderthals dug flint for weapons and tools.

  High-quality flint found in northern France, southern England, and Poland became the raw material for early stone tools. Miners followed seams of the stone underground through shafts and galleries cut into chalk. The mines at Grimes Graves and Krzemionki are especially famous, and like most flint mines they are Neolithic in origin, around 4000 to 3000 BC.

  In pre-Columbian America, Indigenous peoples worked Lake Superior copper from at least 5,000 years ago, leaving behind copper tools and arrowheads that traveled along an extensive trade network. At the Cerillos Mining District in New Mexico, turquoise dated at 700 AD was mined, and an estimated 15,000 tons of rock was removed from Mt. Chalchihuitl using stone tools before 1700.

• 3. Empires Of Gold And Water

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  Ancient Egyptians mined malachite at Maadi, using the bright green stones for ornaments and pottery before larger projects sent expeditions abroad between 2613 and 2494 BC to the Wadi Maghareh region. The gold mines of Nubia were among the most extensive in Ancient Egypt. The Greek author Diodorus Siculus described them and recorded fire-setting, in which miners broke hard rock by heating it.

  The silver mines of Laurium helped sustain Athens, worked by over 20,000 slaves using technology little changed from the Bronze Age. Philip II of Macedon, father of Alexander the Great, seized the gold mines of Mount Pangeo in 357 BC to pay for his armies, and his captured Thracian mines minted coinage at 26 tons per year.

  It was the Romans who built large-scale methods, bringing water to the minehead through aqueducts. They washed away overburden with sudden floods in a process called hushing, then cracked exposed rock with fire-setting and streams of water. In Spain in 25 AD they developed sluicing for alluvial gold, and at Las Medulas seven long aqueducts tapped local rivers. At Dolaucothi they followed veins underground, while at Rio Tinto a sequence of 16 reverse overshot water-wheels in pairs lifted water about 24 meters, worked by miners treading the top slats.

• 4. Powder, Pumps, And Profit

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  The silver crisis of 1465 struck when every mine had reached a depth where shafts could no longer be pumped dry with the available technology. Flooding was the central obstacle of medieval mining, a problem Georg Agricola laid out in detail in De re metallica in 1556. Much of what we know of these techniques comes from that book and from Biringuccio's De la pirotechnia.

  Black powder was first used in mining at Selmecbanya in the Kingdom of Hungary, now Banska Stiavnica in Slovakia, in 1627. Blasting loosened rock far faster than fire-setting and opened ore once thought impenetrable. In 1762 one of the world's first mining academies was founded in the same town.

  Mineral rights split Europe in two. On the continent deposits belonged to the crown under a regalian right that was firmly maintained. In England a judicial decision of 1568 and a law of 1688 restricted royal rights to gold and silver, of which England had almost none. Landlords who owned the iron, zinc, copper, lead, and tin beneath their estates had every reason to dig or to lease. English, German, and Dutch capital financed the work, and in 1642 a colony of 4,000 foreigners was mining and smelting copper at Keswick.

• 5. Booms Across The Continents

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  In Fiji in 1934, the Emperor Gold Mining Company Ltd. began operations at Vatukoula, joined the next year by the Loloma Gold Mines and then Fiji Mines Development Ltd. Gold production rose more than a hundred-fold, from 931.4 ounces in 1934 to 107,788.5 ounces in 1939, an output then comparable to all of New Zealand and Australia's eastern states combined.

  Gold became a major commodity for Africa during the trans-Saharan gold trade from the 7th century to the 14th century, often exchanged for salt. Since the Great Trek of the 19th century, gold and diamond mining in Southern Africa has carried heavy political and economic weight. The Democratic Republic of Congo is the continent's largest diamond producer, with an estimated 12 million carats in 2019.

  In the United States, Congress passed the General Mining Act of 1872 to encourage mining of federal lands, and the California Gold Rush helped drive Westward Expansion. Mining camps grew into cities such as Denver and Sacramento. Australia, by the 1850s, was producing 40 percent of the world's gold, and later opened the Mount Morgan Mine, which ran for nearly a hundred years, along with the Broken Hill ore deposit and the iron ore mines at Iron Knob.

• 6. Cutting Into The Earth

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  Modern surface mining produces 85 percent of minerals in the United States, excluding petroleum and natural gas, and 98 percent of metallic ores. It works by stripping away vegetation, dirt, and bedrock to reach buried deposits. Open-pit mining recovers material from a pit in the ground, quarrying does the same for sand, stone, and clay, and mountaintop removal takes the top off a mountain to reach coal at depth.

  Subsurface mining digs tunnels or shafts to reach ore deeper down. Drift mining uses horizontal tunnels, slope mining uses diagonal shafts, and shaft mining drops straight down. Room and pillar mining leaves pillars to hold up the roof, then often gives way to retreat mining, where those pillars are pulled out as miners withdraw and the room caves in to loosen more ore.

  Ammonium nitrate is the most common explosive in mining. Between 1990 and 1999, about 22.3 billion kilograms of explosives were used in mining, quarrying, and other industries in the United States, with coal mining accounting for 66.4 percent. Some ore is taken without digging at all: in-situ leaching dissolves soluble minerals such as potash and rock salt in place, while copper minerals and uranium oxide need acid or carbonate solutions.

• 7. From Ore To Metal

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  A ton of gold produces 200,000 tons of tailings, because only 5.3 grams of gold come from a ton of ore. Ore mills generate enormous waste, and even copper yields 99 tons of waste per ton of metal. Extractive metallurgy studies how to pull valuable metals from ore, while mineral processing handles the crushing, grinding, and washing that separates them from gangue.

  Placer ore can be cleaned with gravity methods such as sluice boxes, needing only minor shaking to break up sands and gravels. Lode ore demands more: crushing and pulverizing before the valuable minerals can be recovered by mechanical and chemical means. Because most metals sit in ore as oxides or sulfides, they must be reduced, through smelting or, as with aluminium, through electrolytic reduction.

  In 2018, University of Notre Dame researchers led by chemistry professor Bradley D. Smith reported a new class of molecules whose shape and size let them capture precious metal ions. The method converts gold-bearing ore into chloroauric acid and extracts it with an industrial solvent, separating gold without water stripping. The team described it as a milder alternative to a 125-year-old method that treats ore with poisonous sodium cyanide, and noted it could also capture platinum and palladium.

• 8. The Human Cost

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  On the 10th of March 1906, the Courrieres mine disaster killed 1,099 miners in Northern France, Europe's worst mining accident. It was surpassed only by the Benxihu Colliery accident in China on the 26th of April 1942, which killed 1,549 miners. Government figures suggest around 5,000 Chinese miners die in accidents each year, with some reports as high as 20,000.

  In the Democratic Republic of the Congo, cobalt mining has drawn sustained criticism over child labor and deadly conditions. Researcher Siddharth Kara describes miners buried when a pit wall collapsed, reaching a clinic with no antibiotics, no x-ray machine, and only acetaminophen for pain. Workers there earn about two dollars a day. Kara told NPR that displaced families with no other income face a stark choice, asking whether to send a child to school or to dig and eat that day. In December 2019-14 Congolese families filed a lawsuit against the mining company Glencore.

  Uranium mining has fallen heavily on Indigenous communities whose lands lie nearby. In 1987, roughly 50 percent of Native Americans lived in communities with one or more uncontrolled toxic waste sites. Acid mine drainage, formed when sulfide minerals meet air and water, can release acidic runoff carrying arsenic, lead, and mercury for decades after a mine closes. In the United States, the Mining Safety and Health Administration was established in 1978, and miner fatalities fell from 242 that year to 24 in 2019, a figure that points to how much the work has changed and how much remains at stake.