South African diamonds reveal "impossible" chemistry that rewrites Earth’s deep history
By isabelle // 2025-09-29
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  • A rare diamond discovery in South Africa reveals impossible coexisting minerals that rewrite our understanding of Earth’s deep mantle chemistry.
  • Scientists found oxidized carbonates and reduced nickel alloys trapped together in diamonds, proving a long-theorized diamond-forming reaction at unprecedented depths.
  • The find challenges assumptions about mantle oxidation limits and may explain why some diamonds contain nickel, reshaping geology’s core theories.
  • This evidence suggests kimberlite volcanoes originate deeper than believed, carrying diamonds from extreme depths to the surface.
  • The breakthrough highlights the power of independent science to uncover hidden truths, defying institutional skepticism and expanding our knowledge of Earth’s unseen forces.
Deep beneath the surface, where no human has ever ventured, Earth’s mantle churns with mysteries. Now, two unassuming diamonds from a South African mine have cracked open a scientific puzzle, revealing a chemical reaction so unlikely that researchers initially dismissed it as "almost impossible." These gems, formed between 280 and 470 kilometers underground, contain opposing materials that shouldn’t coexist: oxidized carbonates and reduced nickel alloys. Their discovery doesn’t just challenge assumptions about diamond formation; it forces a rewrite of what we know about the mantle’s hidden chemistry. For geologists, diamond inclusions are like tiny time capsules. While jewelers may despise these imperfections, scientists treasure them as the only undisturbed samples from Earth’s deep interior. The two diamonds in question, unearthed from South Africa’s Voorspoed mine, trapped something extraordinary. One contained carbonate minerals rich in oxygen (oxidized), while the other held nickel-iron alloys devoid of it (reduced). Normally, these substances react and neutralize each other, much like an acid and a base. Finding them preserved together was so baffling that Yaakov Weiss, senior lecturer at Hebrew University of Jerusalem, and his team shelved the samples for a year before revisiting them.

A snapshot of the seemingly impossible

The breakthrough came when researchers realized these inclusions weren’t just random; they were frozen mid-reaction. "It’s basically two sides of the [oxidation] spectrum," Weiss explained. The diamonds had captured the exact moment when carbonate fluids, dragged downward by subducting tectonic plates, met the mantle’s metal-rich depths. This interaction is now confirmed as a key diamond-forming process, one previously only theorized through models and lab experiments. What makes this find revolutionary is its depth. Until now, scientists believed oxidized materials couldn’t exist much below 300 kilometers. Yet these diamonds, formed far deeper, prove otherwise. This suggests that kimberlites—the volcanic rocks that carry diamonds to the surface—might also originate from greater depths than assumed. Maya Kopylova, a geoscientist at the University of British Columbia, noted that such samples are rare. "What happened below 200 km was just our idea, our models," she said, because direct evidence was lacking. Now, that evidence exists.

Nickel’s mysterious role in diamond crystal structures

The discovery may also solve another long-standing riddle: why some diamonds contain trace amounts of nickel, an element far heavier than carbon. Nickel atoms occasionally replace carbon in a diamond’s crystal lattice, a phenomenon that has puzzled scientists. Kopylova speculated that this new data could explain it. "That would be very interesting to investigate further," she said. If diamonds form at depths where nickel alloys are stable, the element’s presence in their structure suddenly makes sense. Beyond diamonds, these findings reshape our understanding of mantle dynamics. The reaction captured in the inclusions—a "redox-freezing" event—suggests that localized oxidation can occur deep underground when carbon-rich melts infiltrate reduced rocks. This process may prime the mantle for future volcanic activity, including the eruptions that bring diamonds (and kimberlites) to the surface. In essence, these tiny inclusions hint at vast, unseen forces shaping Earth’s geology over billions of years.

Why this matters beyond the lab

This discovery isn’t just academic. It underscores the value of independent scientific inquiry, free from the constraints of institutional dogma. For decades, theoretical models predicted nickel alloys at these depths, but without physical proof, skepticism lingered. Now, nature has provided the evidence—delivered via two diamonds that defied expectations. The implications stretch further still. If oxidized materials exist deeper than once thought, it could influence everything from our understanding of volcanic activity to the recycling of Earth’s crust. It also highlights how little we truly know about the planet beneath our feet. In an era where centralized narratives often dominate scientific discourse, findings like these remind us that truth can emerge from the most unexpected places—even the flaws in a diamond. Sources for this article include: LiveScience.com ScientificAmerican.com ScienceDaily.com
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