Mineral Rights, Net

The Partnership’s mineral rights consist of the following:



	December 31, 2018
(In thousands)	Carrying Value		Accumulated Depletion			Net Book Value
Coal properties	$	1,164,845	$	(451,210	)	$	713,635
Aggregates properties	24,920		(11,814		)	13,106
Oil and gas royalty properties	12,395		(7,632		)	4,763
Other	13,158		(1,550		)	11,608
Total mineral rights, net	$	1,215,318	$	(472,206	)	$	743,112



	December 31, 2017
(In thousands)	Carrying Value		Accumulated Depletion			Net Book Value
Coal properties	$	1,170,104	$	(436,964	)	$	733,140
Aggregates properties	37,942		(9,602		)	28,340
Oil and gas royalty properties	12,395		(7,158		)	5,237
Other	13,168		(1,466		)	11,702
Total mineral rights, net	$	1,233,609	$	(455,190	)	$	778,419

Depletion expense related to the Partnership’s mineral rights is included in Depreciation, depletion and amortization on the Partnership's Consolidated Statements of Comprehensive Income and totaled $17.0 million, $20.1 million and $27.8 million for the year ended December 31, 2018, 2017 and 2016, respectively.

Sales of Mineral Rights

During the year ended December 31, 2018, the Partnership sold mineral reserves in its Coal Royalty and Other segment in multiple transactions for cumulative gross proceeds of $2.4 million and recorded a cumulative gain of $2.4 million included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income.

During the year ended December 31, 2017, the Partnership sold mineral reserves in its Coal Royalty and Other segment in multiple transactions for cumulative gross proceeds of $1.0 million and recorded a cumulative gain of $3.5 million included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income.

During the year ended December 31, 2016, the Partnership sold the following assets:

1)Oil and gas royalty and overriding royalty interests in the Coal Royalty and Other segment in several producing properties located in the Appalachian Basin for $36.4 million gross sales proceeds. The effective date of the sale was January 1, 2016, and the Partnership recorded an $18.6 million gain from this sale included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income.

2)Aggregates reserves and related royalty rights in the Coal Royalty and Other segment at three aggregates operations located in Texas, Georgia and Tennessee for $10.0 million gross sales proceeds. The effective date of the sale was February 1, 2016, and the Partnership recorded a $1.5 million gain from this sale included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income.

In addition to the two asset sales described above, during the year ended December 31, 2016, the Partnership sold mineral reserves within its Coal Royalty and Other segment in multiple sale transactions for $17.3 million of cumulative gross sales proceeds and recorded a cumulative gain of $8.6 million from these sale transactions that are included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income. These amounts primarily relate to eminent domain transactions with governmental agencies and the sale of additional oil and gas royalty interests.

Impairment of Mineral Rights

During the years ended December 31, 2018, 2017 and 2016, the Partnership identified facts and circumstances that indicated that the carrying value of certain of its mineral rights exceed future cash flows from those assets and recorded non-cash impairment expense included in Asset impairments on the Consolidated Statements of Comprehensive Income as follows:



	For the Years Ended December 31,
(In thousands)	2018		2017		2016
Coal properties ⁽¹⁾	$	5,259	$	595	$	12,088
Oil and gas properties	—		—		36
Aggregates and timber royalty properties⁽²⁾	13,021		2,372		1,677
Total	$	18,280	$	2,967	$	13,801

(1)

The Partnership recorded $5.3 million of coal property impairments during the year ended December 31, 2018 primarily as a result of lease terminations, of which it recorded $5.0 million of impairment expense to fully impair certain coal properties during the three months ended December 31, 2018. The Partnership recorded $0.6 million of coal property impairments during the year ended December 31, 2017. The Partnership recorded $12.1 million of coal property impairments during the year ended December 31, 2016 primarily as a result of lease surrender and termination. The Partnership recorded $3.8 million of coal property impairment during the three months ended September 30, 2016 and the fair value of the impaired asset was reduced to $4.0 million at September 30, 2016. The Partnership recorded $8.2 million of impairment expense to fully impair certain coal property impairment during the three months ended December 31, 2016.

(2)

During the three months ended December 31, 2018, the Partnership recorded $13.0 million of impairment expense related to an aggregates property that the Partnership owns and leases to its former construction aggregates business, which mines, produces and sells the aggregates. The fair value of the impaired asset was reduced to $2.3 million at December 31, 2018. The Partnership recorded $2.4 million and $1.7 million of aggregates and timber royalty properties impairments during the year ended December 31, 2017 and 2016, respectively.