PROPERTY, PLANT, EQUIPMENT AND MINERAL PROPERTIES

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT, EQUIPMENT AND MINERAL PROPERTIES

PROPERTY, PLANT, EQUIPMENT, AND MINERAL PROPERTIES

"Property, plant, equipment, and mineral properties, net" were comprised of the following (in thousands):

	December 31,
	2020		2019
Land	$	27,263	$	27,274
Ponds and land improvements	67,843		65,992
Mineral properties and development costs	143,955		143,988
Buildings and plant	81,692		81,468
Machinery and equipment	265,121		253,536
Vehicles	5,919		6,222
Office equipment and leasehold improvements	9,083		9,136
Operating lease ROU assets	9,622		8,123
Breeding stock	260		—
Construction in progress	1,710		7,124
Total property, plant, equipment, and mineral properties, gross	$	612,468	$	602,863
Less: accumulated depreciation, depletion, and amortization	(256,971)		(224,354)
Total property, plant, equipment, and mineral properties, net	$	355,497	$	378,509

We incurred the following expenses for depreciation, depletion, and amortization of ROU assets, including expenses capitalized into inventory, for the following periods (in thousands):

	Year Ended December 31,
	2020		2019		2018
Depreciation	$	29,697	$	27,889	$	27,858
Depletion	3,952		4,173		4,357
Amortization of ROU assets	2,139		2,059		—
Total incurred	$	35,788	$	34,121	$	32,215