Segment information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting [Line Items]
Exploration and development costs	$ 8,554	$ 2,344	$ 18,206	$ 5,343
Mine site costs	3,879	2,673	9,322	5,153
Reportable Segment
Segment Reporting [Line Items]
Exploration	6,467	877	14,098	1,863
Technical and projects	513	420	1,215	794
Mine maintenance	384	413	884	780
Processing maintenance	679	555	1,347	1,100
Site-level general and administrative	4,390	2,752	9,984	5,959
Exploration and development costs	8,554	2,344	18,206	5,343
Mine site costs	3,879	2,673	9,322	5,153
Segment expenses	$ 12,433	$ 5,017	$ 27,528	$ 10,496

Exploration expenses (including prospecting) related to oil and gas producing entities and would be included in operating expenses of that entity. Costs incurred in identifying areas that may warrant examination and in examining specific areas that are considered to have prospects of containing oil and gas reserves, including costs of drilling exploratory wells and exploratory-type stratigraphic test wells. Exploration costs may be incurred both before acquiring the related property (sometimes referred to in part as prospecting costs) and after acquiring the property. Principal types of exploration costs, which include depreciation and applicable operating costs of support equipment and facilities and other costs of exploration activities, are: (i) Costs of topographical, geographical and geophysical studies, rights of access to properties to conduct those studies, and salaries and other expenses of geologists, geophysical crews, and others conducting those studies. Collectively, these are sometimes referred to as geological and geophysical or "G&G" costs. (ii) Costs of carrying and retaining undeveloped properties, such as delay rentals, ad valorem taxes on properties, legal costs for title defense, and the maintenance of land and lease records. (iii) Dry hole contributions and bottom hole contributions. (iv) Costs of drilling and equipping exploratory wells. (v) Costs of drilling exploratory-type stratigraphic test wells.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 932
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477215/932-235-50-28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 932
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477215/932-235-50-28

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 932
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 23
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477215/932-235-50-23

Name:	us-gaap_ExplorationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration