By Rose Schreiber

Can we imagine the Earth over two billion years ago, some 2060 million years in the past?

Nearly half the Earth’s lifetime.

What was it like?

The pink-hued oceans, the fragmentary landmasses.

No plants or animals yet, but there is oxygen in the air, released over hundreds of millions of years by cyanobacteria.

From this oxidation, massive climatic and geologic shifts are underway: the Earth has cooled dramatically, precipitating the first ice ages, and there has been an explosion of newly evolved, oxidized mineral species. How can it be? Tiny, microscopic lifeforms—some of Earth’s first—definitively upending an entire planet’s chemistry, climate, and geology. These changes would ricochet into the present. But for now, this is the Rhyacian, the second geologic period in the Paleoproterozoic. Both above and below ground, magma flows profusely. 

In the interior of the Earth’s crust, molten rock is pressing upwards from the mantle, pooling, and slowly crystallizing. These are igneous intrusions—underground pockets of magma filling and widening any voids in the wall rock around them. Over the course of five million years, from 2060 to 2055 Ma, vast quantities of magma come in waves. The result: a colossal, layered deposition, a growing, dynamic mass that is alternately cooling and heating, its pressure rising and falling. Different minerals precipitate out of the changing temperatures and pressures. Stratigraphic lines appear, colored by platinum, iron, and chrome. The molten rock cools. The formation is wide and thick: it stretches over 25,000 square miles; it runs more than five miles deep. 

This geologic formation is known, in our time, as the Bushveld Igneous Complex, and it is located in northeast South Africa. The Bushveld is the largest layered igneous intrusion in the world and it is full of mineral-rich ore, including large seams of chromite. It is estimated that as much as 90% of the world’s chromite reserves—more than 11 billion metric tons—are located in this one region. A vast proportion of the world’s chrome supply is extracted here. Demand for chrome has skyrocketed, driven by industrialization and stainless steel. 

The Bushveld, as a whole, is highly exploited; it is full of mining operations extracting platinum, palladium, vanadium, iron, uranium, tin, and chromium. Imagine these mines as a complex network: a cultural and political sphere, a mining ecology and geology. There are frequent, and long running, strikes by Bushveld miners, strikes that are, themselves, highly dangerous: in 2012, the South African Police Service opened fire on striking Bushveld platinum miners, killing 34 and injuring 78, in what became known as the Marikana massacre. Contamination and run-off in this region are also major social and environmental issues. Even the physical processes of Bushveld mining are deeply entangled: some chromium mining operations are built around the waste products and tailings of other mines. As fine chrome is brought to the surface and discarded by platinum producers, chrome miners move in—some legal, some not. Alongside the excavation we know, is the excavation we don’t know: an entire illegal web of chrome extraction and distribution starts here. As much as 10% of South Africa’s chromium ore flows into a parallel, underground stream. Now, what once took five million years—the slow deposition and emplacement of chromite—takes a mere handful: geologic processes accelerated and replaced by anthropogenic deposits and displacements. 

Not all of our chrome comes from this place; in fact, like many raw materials, chrome appears to change hands several times along the global industrial pipeline. Other sources of chrome flow into a single, mixed channel, and the problem is compounded by chromium traffickers operating in the shadows. We know this: much of the chromite mined in South Africa flows to China for use in stainless steel. From Chinese refinement plants, chrome oxide is shipped around the world. Chrome connects us to a deep time geologic past, as well as a more shallow geologic present: two billion years of formation and tectonic shifts, now caught in the gears of the Anthropocene.