It has been an arduous journey for long-standing shareholders like me, but Foolish patience has begun to pay off in spades following a seminal moment in one junior miner's quest to ascend into the class of midtier miners.

I have characterized Taseko Mines (AMEX:TGB) as a David among Goliaths; a commensurate underdog in a copper industry dominated by global megaminers like Southern Copper (NYSE:PCU) and Freeport-McMoRan Copper & Gold (NYSE:FCX). Well, David just had a growth spurt, and may soon be crowned King Midas.

Taseko announced Friday that the Prosperity copper and gold project has received the environmental permits from the British Columbia provincial authorities needed for construction to proceed later this year. Featuring massive deposits like Seabridge Gold's (AMEX:SA) KSM and Silver Standard Resources' (NASDAQ:SSRI) Snowfield -- together accounting for nearly 60 million ounces of untapped gold in the ground -- British Columbia continues to warrant the careful attention of discerning mining investors.

Following a two-year, $775 million construction phase, Taseko looks forward to a 20-year mine life, with an internal rate of return of 30% (using gold at $900 and copper at $2 as the basis).

With one of the most attractive cost profiles this Fool has ever seen, the Prosperity project earns its name with an estimated production cost of negative $330 per ounce of gold after copper byproduct credits! Taseko could enjoy some of the heftiest operating margins of any gold producer in the world, better than even low-cost leaders like Yamana Gold (NYSE:AUY) and Goldcorp (NYSE:GG). Multiply those kinds of margins by 7.7 million ounces of recoverable gold in reserve, and you may grasp a taste of the miner's cash flow potential.

Meanwhile, Taseko has attracted a loyal Motley Fool CAPS following based on its low-cost copper production and well-executed growth strategy at its flagship Gibraltar copper and molybdenum mine. Even after selling a 25% stake in Gibraltar to fund mine development at Prosperity, Gibraltar remains a lucrative cash-flow generator that will aid the company through the mine construction phase.

The Prosperity project has been under some form of environmental review since 1995, and the market took notice once the permit was granted. Shares rose 15% Friday to trade above $5 for the first time since mid-2008, and rose a further 13% on the Toronto exchange Monday (while U.S. markets were closed). All told, Taseko shares have gained more than 350% since I asked Fools to take a fresh look at the stock in October 2008, but I still believe in the potential for further upside.

I perceive the smart money will begin to recognize that junior miners and explorers represent one of the last frontiers of both deep value and exciting growth potential under these economic circumstances. In the context of a continuing long-term secular bull market for commodities, and persistent fiscal imbalances among developed Western economies to buoy gold prices, I see Taseko shares primed for sustained strength. Less than two months ago, I offered Taseko Mines as the best bargain in miners, and it will take far more than a two-day surge in price to mine all the value from these underpriced shares.

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Fool contributor Christopher Barker is the commodore of copper and the Colonel Klink of zinc. He can be found blogging actively and acting Foolishly in the CAPS community under the user name TMFSinchiruna. He tweets. He owns shares of Freeport-McMoRan Copper & Gold, Silver Standard Resources, Taseko Mines, and Yamana Gold. The Fool's disclosure policy is worth way more than $3.44 per pound.