Cloud Peak started 2013 with about 1.3 billion tons of coal reserves. That's a drop in the bucket compared to industry heavyweight Peabody Energy (NYSE: BTU ) , which had reserves of around 9.3 billion tons. Alpha Natural Resources (NYSE: ANR ) and Arch Coal (NYSE: ACI ) , numbers two and three in the industry, had reserves of 4.6 billion tons and 2.1 billion tons, respectively.

The agreement with the Crow Tribe, assuming all 1.4 billion tons goes into the proved and probable category, more than doubles Cloud Peak's reserves and vaults it into third place on the reserve list. That said, all 2.7 billion tons of Cloud Peak's coal will be thermal; Alpha's thermal reserves account for just 3.1 billion of its total. Cloud Peak has clearly become a much heavier hitter in the thermal category.

That said, the Crow land is far from developed. Bringing the mining operation up to speed could take several years. So the purchase is good longer term, but look for Cloud Peak's capital investments to be higher than they might have otherwise been for a few years. That's a negative aspect of this deal based on the current coal environment, since prices are depressed and cost cutting has been an industrywide focus.