Recently we reported on some rather remarkable findings: that an ancient gold trade route had been uncovered between Ireland and Britain dating back to the Bronze Age in 2500 B.C. But lost in all the shuffle is the fact that these prehistoric Brits didn’t appear to care about gold — but why? Well, there’s a very interesting answer.

Researchers found that much of the ancient gold found in museum collections in Ireland originated in Cornwall, which boasted some of the richest gold mines in the land. But the researchers also found that Cornwall didn’t focus on gold production, the gold they mined was merely a byproduct of an industry that was of far greater importance to them: the extraction of the exotic material known as … tin.

In fact, Brits didn’t focus on gold at all, it was just a nice little bonus that they were happy to ship to the Irish, according to an Independent report. The miners were instead trying to extract tin from the rivers through panning or damming and sluicing systems, much like gold is panned for today.

As they searched for this tin, naturally the gold also turned up, and they used woolly sheepskins to sift through the tiny grains of metals. This might have led to the ancient Greek mythological concept of the Golden Fleece, according to the report.

So why was tin so important, though? Tin is crucial in the production of bronze, as in order to make it, metalworkers must combine the metal along with copper. The Brits’ obsession with bronze is why we come to know it as the Bronze Age. And there was no better place to get tin than in areas near Cornwall, where rivers had eroded the tin — as well as the gold — from exposed granite landscapes.