Shares of Canadian junior miner Peregrine Metals Ltd. are soaring after Stillwater Mining Ltd. agreed to pay a staggering premium for the Vancouver-based company.

Stillwater, the U.S. platinum giant, is paying US$487.1-million in cash and stock for Peregrine, or about $3.16 a share. Peregrine shares, which closed at just 81¢ last Friday, were up 250% on $2.84 on Monday morning. The deal gives Stillwater the Altar copper-gold project in Argentina.

In explaining the premium, Stillwater chairman and chief executive Frank McAllister said on a conference call that he valued Peregrine at 3.8¢ per pound of copper resources, which is in line with recent transactions in the sector.

However, the share price premium is higher than any copper merger in recent memory.

“We’re looking at it from the miner’s perspective rather than the financial markets perspective,” he said.