INTANGIBLE ASSETS

The components of intangible assets for the years ended December 31, 2016 and 2015, were as follows (amounts in thousands):



	Weighted- Average Useful Lives (in Years)	2016			2015
Amortizable intangible assets:
Customer relationships	10.7	$	13,171		$	13,413
Patents, trademarks, and other	8.1	14,629			13,237
Total at cost		27,800			26,650
Less accumulated amortization		(11,399		)	(8,852		)
		$	16,401		$	17,798

Amortization related to intangible assets for the years 2016, 2015, and 2014 totaled $2.2 million, $3.0 million, and $4.4 million, respectively.

The estimated aggregate amortization expense at December 31, 2016, for each of the years (or other periods) set forth below is as follows (amounts in thousands):



2017	$	2,063
2018	2,000
2019	2,000
2020	2,000
2021	1,261
Thereafter	7,077
	$	16,401

As a result of the continued downturn in the mining industry through 2016, the Company tested the Australian intangibles for impairment during the fourth quarters of both 2016 and 2015. The Australian intangibles totaled $9.1 million and $10.1 million at December 31, 2016 and 2015, respectively, and consist primarily of customer relationships. No impairment was indicated in either period.