For all the bullish talk about metals of the future, miners are making some of their biggest profits from heavy-industry stalwart coal.

Base metals from copper to zinc have tumbled this year, caught up as a proxy for trade fears and emerging market jitters. Meanwhile, coal has ground steadily upwards, supported by strong demand from top commodities user China, and is trading near the highest it has traded at in more than six years.

That is translating into big paydays for producers. Glencore is in touching distance of seeing its coal mining profits eclipse copper earnings this year for the first time since it sold shares in London in 2011. Anglo American’s coal earnings almost trebled in the past four years, despite lower production. The fuel is forecast to contribute a whopping 43% of Anglo’s profits this year, despite it operating some of the best platinum, diamond and copper mines in the world.

“This is the sweet spot for the coal miners,” says Ben Davis, an analyst at Liberum Capital Markets. “Chinese coal demand is through the roof and that’s because, domestically, they’re not producing enough. China is importing more coal than it ever has done before.”

It was not supposed to be this way. Almost everyone in metals is universally bullish about copper, from the CEOs of the biggest mining companies to investors and analysts, all expecting increased demand from the electrification of cities and cars and constrained supply. Coal, on the other hand, has been widely shunned by both investors and many producers.

One explanation is that coal is susceptible to strong price swings. Unlike most other commodities, the bulk of the fuel is produced in the country where it is burned, near power stations. The global seaborne market of about one-billion tons is less than a fifth of total production, which means small swings in demand can have a disproportionate impact on price.

Seaborne coal demand increased more than 9% in the first half, while supply rose by less than 8%, according to Glencore. Chinese coal power generation increased by 7.8%.

While a disconnect between bulk materials and base metals is not uncommon – commodities like coal and iron-ore tend to be more closely aligned with supply and demand fundamentals than investor sentiment – the pattern is holding for longer than usual.

“We have seen such disconnects before; however, they have tended to last only a few weeks,” says BMO Capital Markets. “The current example has lasted several months, and every time it looks as though the macro headwinds have blown themselves out, they return once more.”