Martin Frobisher
On his second voyage, Frobisher found what he thought was gold ore and carried 200 tons of it home on three ships since initial assaying determined it to be worth a profit of £5.10 per ton. Encouraged, Frobisher returned to Canada with an even larger fleet and dug several mines around Frobisher Bay. He carted 1,350 tons of the ore back, but after years of smelting, it was realised that both that batch of ore and the earlier one he had taken had been worthless iron pyrite.