Big mining companies BHP Group and Rio Tinto dropped sharply on June 26, 2026. The reason wasn't anything wrong with their mines. Instead, two other things happened at the same time: the US dollar got stronger, and investors suddenly got worried that tech companies won't spend as much money as expected on building data centers, The Wall Street Journal reported.

The dollar problem. Metals like copper and iron ore are bought and sold around the world using US dollars as the standard currency. When the dollar gets stronger, miners get fewer dollars for the same amount of metal. Think of it like a restaurant owner in another country who gets paid in dollars for meals—when the dollar strengthens against their local currency, those dollars are worth less in their home economy.

The AI problem. Over the past year, mining stocks rose partly because investors believed that data centers powering artificial intelligence would need massive amounts of copper for power cables and infrastructure. If tech companies spend less on these data centers, demand for copper falls, and mining stocks take a hit. The Nasdaq (a stock index heavy in tech) fell about 1.61% on June 23, led by AI and semiconductor names, NBC News reported. Weakness spread from the US into Asian markets. The selling got worse when the Federal Reserve said interest rates would stay high for longer than investors hoped, Reuters noted.

Why interest rates matter. When interest rates are high, money today is worth more than money in the future (because you can earn more by saving it). This affects how much investors will pay for companies whose big profits come years from now. AI infrastructure—massive spending on data centers—won't make money for a long time. So when the Federal Reserve signals rates will stay high, that long-delayed payoff looks less attractive, and investors want to pay less for those stocks today.

This isn't the first time this doubt appeared. In late 2025, Reuters reported, AI stocks had already dropped when investors started asking harder questions about when all that spending would actually produce profits. What happened in June 2026 is the market revisiting the same uncertainty.

Mining companies got hit especially hard because two things worked against them at once: the dollar was stronger and investors became less confident about copper demand from AI data centers. Usually in a market downturn, either prices fall or the amount people want to buy falls—but not both at the same time. Mining stocks faced both at once.

Does this mean copper demand from AI won't happen? No. Data centers do use more copper, and that trend is real. But how fast it will grow, and whether it will be enough to make up for weakness in other parts of the global economy, is still genuinely uncertain. When stocks fell, investors seemed to be changing their guess about how fast copper demand would grow—not deciding it won't happen at all.

The bigger picture here is worth noticing: when the Nasdaq fell by less than 2%, it was enough to push down mining stocks with operations spread across the entire world. That shows how much more connected global stock markets have become. Traditional ideas about splitting investments across different sectors or industries to reduce risk may not work the way they used to.