v3.26.3
Basis of Preparation - Schedule of Organization, Consolidation and Ownership of Subsidiaries (Details)
 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
0896800 BC Ltd. (0896800) [Member]    
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]    
Jurisdiction of incorporation British Columbia, Canada  
Ownership 100.00% 100.00%
Elk Creek Resources Corp. (ECRC) [Member]    
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]    
Jurisdiction of incorporation [1] Delaware, USA  
Ownership [1] 81.33% 80.42%
NioCorp Advanced Metals and Alloys, LLC (NAMA) [Member]    
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]    
Jurisdiction of incorporation Delaware, USA  
Ownership 100.00% 0.00%
NioCorp Technologies Limited [Member]    
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]    
Jurisdiction of incorporation United Kingdom  
Ownership 100.00% 100.00%
[1] Represents 100% of Class A common stock owned by 0896800, and 3,516,140 and 3,934,031 Vested Shares and 3,391,596 and 3,391,596 Earnout Shares (each as defined below) held by third parties, and outstanding as of June 30, 2026 and 2025, respectively.