Northern Dynasty Minerals' (NYSEMKT:NAK) giant Pebble copper and gold mine project in Alaska was given a new lease on life following the election of Donald Trump. After stalling under the previous administration, permitting appears to be back on track for this upstart miner. Most people are caught up in the potential size of the mine, but that's not the real reason to love Northern Dynasty Minerals stock.

It's pretty big

To be honest, size is definitely an important factor with the Pebble project. According to Northern Dynasty's estimates, the mine could be the largest undeveloped copper and gold resource in the world. It believes there's as much as 57 billion pounds of copper, 70 million ounces of gold, 3.4 billion pounds of molybdenum, and 344 million ounces of silver in the mine. Those figures could be on the low side, too, if the company is lucky.

The ends of copper pipes.

Image source: Getty Images

Just to give you a reference point, Freeport McMoRan (NYSE:FCX) is one of the world's largest copper miners. This giant copper miner's North American operations hold 30 billion pounds of copper spread across seven mines. Pebble could be larger than all seven combined. In Indonesia, there are around 26 billion pounds of copper and 25 million ounces of gold in Freeport's Grasberg mine. Again, Pebble could best those numbers if Northern Dynasty's estimates prove accurate. Pebble could be a pretty big opportunity.    

The Pebble estimates, however, have to be taken with a grain of salt. Since Northern Dynasty's Pebble project is still in the early stages of development, there's no certainty that all of the copper and gold it thinks is there will, in fact, be there. That, however, is the risk you take on when you buy a miner that's in the development stage.

More than size

So size is important here in a number of ways. But there's another issue to take a look at... cost. If Northern Dynasty Minerals' estimates are correct, the Pebble mine could be among the cheapest copper mines in the world, sitting in the middle of the first quartile on the cost curve. The current estimate is that the mine could have a cash cost of as little as $0.53 per pound of copper.    

A graph of the copper cost curve showing the Pebble mine in the middle of the first quartile.

Northern Dynasty's estimates of Pebble's cash costs are industry leading. Image source: Northern Dynasty Minerals 

Freeport's Grasberg is cheaper, but most other major mines have cash costs of more than $1 per pound of copper. The current price of copper on the spot market is well over $2 per pound. In other words, this could turn out to be a very profitable copper mine, even if copper prices are lower than they are today. And that's the real reason why investors should love Northern Dynasty Minerals -- a large, high cost mine simply wouldn't be as viable as a large, low cost mine.    

Early days

Now, that said, Northern Dynasty Minerals' Pebble project is a long way off from being completed. It's just working off of estimates today. For example, the size of the copper deposit is measured and indicated reserves, not proven and probable. Essentially, the miner thinks it can get at those materials, but until the mine is further along in the development process it won't know for sure. As for costs, those, too, are just estimates today and could prove wrong.

In short, this is not an investment for conservative investors. However, if you can stomach the risk of investing in a mine project that won't start producing until at least 2024, make sure you pay attention to the potential size and costs. It's the latter that will get Pebble up and running. Size alone isn't enough.    

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.