| Property, Plant and Equipment |
| | | | | | | | | | June 30, 2013 | | December 31, 2012 | Coal and other plant and equipment | $ | 6,086,734 |
| | $ | 6,030,620 |
| Intangible drilling cost | 1,721,384 |
| | 1,550,297 |
| Proven gas properties | 1,597,626 |
| | 1,596,838 |
| Coal properties and surface lands | 1,455,541 |
| | 1,346,151 |
| Unproven gas properties | 1,371,532 |
| | 1,266,017 |
| Gas gathering equipment | 1,034,927 |
| | 1,006,882 |
| Airshafts | 727,674 |
| | 706,388 |
| Mine development | 583,494 |
| | 537,939 |
| Leased coal lands | 529,700 |
| | 529,758 |
| Gas wells and related equipment | 542,284 |
| | 492,367 |
| Coal advance mining royalties | 396,034 |
| | 391,501 |
| Other gas assets | 125,194 |
| | 82,217 |
| Gas advance royalties | 22,127 |
| | 8,229 |
| Total Property Plant and Equipment | 16,194,251 |
| | 15,545,204 |
| Less: Accumulated DD&A | 5,770,506 |
| | 5,354,237 |
| Total Net PP&E | $ | 10,423,745 |
| | $ | 10,190,967 |
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