What happened

Turquoise Hill Resources (TRQ) stock ripped higher this morning, jumping 24.9% as of 10:20 a.m. ET. The Canada-based copper miner, which recently rejected a mega buyout offer, has now received a much bigger offer, and that's sent the markets into a tizzy.

So what

Mining giant Rio Tinto (RIO 1.57%) has been pursuing Turquoise Hill Resources since March when it first offered to acquire a 49% stake in the miner for 34 Canadian dollars (roughly $26.57) per share, in a deal valued at $2.7 billion.

Turquoise Hill Resources rejected the offer, claiming the price offered didn't reflect the "full and fair" value of the miner.

Not one to relent, Rio Tinto sweetened its bid this morning and has now offered Turquoise Hill a price of CA$40 per share, or roughly $3.1 billion in total. Shares of the Canadian miner surged as the market reacted to Rio Tinto's new offer.

Rio Tinto stock, on the other hand, was down about 3.5% on Wednesday, as of this writing.

Rio Tinto already owns a majority stake in Turquoise Hill. By taking the company private, Rio Tinto wants to gain full control over Oyu Tolgoi, one of the world's largest copper and gold deposits, which recently received the government of Mongolia's approval to begin operations after a long-drawn dispute. The government owns a 34% stake in the mine, while Turquoise Hill owns the remaining.

Now what

Rio Tinto estimates Oyu Tolgoi to be among the five largest copper mines in the world once it starts underground mine operations. Oyu Tolgoi is expected to produce an average of 500,000 tons of copper per year between 2028 and 2036. That's precisely how much the world's fifth-largest copper mine, Cerro Verde in Peru, owned by Freeport McMoRan, currently produces.

It's easy to see why Rio Tinto is so desperate to acquire Oyu Tolgoi: Copper is a red-hot commodity, and Oyu Tolgoi will significantly strengthen the mining giant's foothold in the copper industry. Copper prices hit all-time highs in March as demand from key end markets, particularly electric vehicles and renewable energy (wind and solar), rocketed. S&P Global projects the demand for copper to nearly double by 2035.