Note 11 - Segment Reporting - Reconciliation of operating profit and capital expenditure (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)
SEGMENT REPORTING
Number of Operating Segments			1
Number of Reportable Segments			1
Cash cost of sales (FOB mine)	$ 110,905,000	$ 98,469,000	$ 203,669,000	$ 207,937,000
Transportation costs	20,673,000	22,872,000	39,671,000	51,748,000
Alternative mineral development costs	1,918,000	1,124,000	3,830,000	2,255,000
Other cost of sales	686,000	305,000	1,144,000	543,000
Cost of sales	134,182,000	122,770,000	248,314,000	262,483,000
Total capital expenditures (including accrued capital expenditures and capitalized interest)	$ 14,428,000	$ 21,265,000	$ 35,880,000	$ 41,194,000