PROPERTY, PLANT, EQUIPMENT, AND MINERAL PROPERTIES (Schedule of Property, Plant, Equipment, and Mineral Properties) (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	$ 715,080	$ 701,039
Less: accumulated depreciation, depletion, and amortization	(419,668)	(402,283)
Total property, plant, equipment and mineral properties, net	295,412	298,756
Land [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	519	519
Ponds and Land Improvements [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	88,117	87,881
Mineral Properties And Development Costs [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	157,649	155,221
Buildings and Plant [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	99,010	97,924
Machinery and Equipment [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	332,882	324,327
Vehicles [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	8,507	8,061
Office Equipment and Improvements [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	9,497	10,000
Operating Lease ROU Assets [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	3,181	3,181
Construction in Progress [Member]
Property, Plant, and Equipment [Line Items]
Total property, plant, equipment, and mineral properties, gross	$ 15,718	$ 13,925