Property, Plant and Equipment, net

9 Months Ended

12 Months Ended

Sep. 30, 2016

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

6. Property, Plant and Equipment, net

Net property, plant and equipment consists of:


	September 30, 2016		December 31, 2015
Machinery, equipment and tooling	$	4,809	$	4,673
Vehicles		953		952
Furniture and fixtures		303		303
Plant and building		64,387		64,001
Real estate properties		3,504		3,500
Railroad and sidings		7,920		7,868
Land and improvements		13,317		12,977
Asset retirement obligation		1,135		1,135
Mineral properties		9,785		9,785
Deferred mining costs		417		155
Construction in progress		16,517		16,637

		123,047		121,986
Less: accumulated depreciation and depletion		17,752		13,058

Total property, plant and equipment, net	$	105,295	$	108,928

Depreciation expense was $1,647 and $1,393 for the three months and $4,821 and $3,682 for the nine months ended September 30, 2016 and 2015, respectively.

The Company capitalized $0 and $541 for the three months and $139 and $1,520 for the nine months ended September 30, 2016 and 2015, respectively, of interest expense associated with the construction of new plant and equipment.

5. Property, Plant and Equipment

Property, plant and equipment consists of the following at December 31, 2015 and 2014:


	2015		2014
Machinery, equipment and tooling	$	4,673	$	4,011
Vehicles		952		733
Furniture and fixtures		303		206
Plant and building		64,001		43,785
Real estate properties		3,500		2,131
Railroad and sidings		7,868		7,193
Land and improvements		12,977		9,132
Asset retirement obligation		1,135		1,748
Mineral properties		9,785		9,734
Deferred mining costs		155		—
Construction in progress		16,637		14,941

		121,986		93,614
Less: accumulated depreciation and depletion		13,058		7,799

Property, plant and equipment, net	$	108,928	$	85,815

Depreciation expense was $5,276 and $3,611 for the years ended December 31, 2015 and 2014, respectively. Depletion expense was $13 and $14 for the years ended December 31, 2015 and 2014, respectively. The Company capitalized $1,808 and $453 of interest expense associated with the construction of new plant and equipment for the years ended December 31, 2015 and 2014, respectively.