Canadian base-metals producer First Quantum Minerals (OTC:FQVLF) yesterday made another unsolicited offer to buy out fellow Canadian miner Inmet Mining (UNKNOWN:IEMMF.DL), increasing its previous offer by about 2.8% per share. The latest proposal values Inmet Mining at about C$5.1 billion, and shareholders could elect to be paid in all cash, all stock, or a 50-50 mix.

The C$5.1 billion valuation works out to C$72.00 per share, up from a C$70-per-share offer late last month.

Inmet issued a press release today saying that no official offer had yet been received, and that the company would make no further public statements on the proposal until the Board of Directors had reviewed it.

First Quantum said the acquisition could make the combined company one of the world's five largest copper producers within five years, and that the two companies were "uniquely complementary" to one another.

Inmet has already rebuffed two similar offers from First Quantum , the first one on Nov. 1 for C$62.50 per Inmet share, the second on Nov. 28 for C$70 per share. The third and most recent offer comes after Inmet's Dec. 13 announcement that its total estimated copper reserves jumped 27%, and total estimated gold increased 41%.

Shares of Inmet are up more than 4% on the news, while shares of First Quantum were trading nearly 2% lower on Monday.