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Cover - shares
 6 Months Ended
Dec. 31, 2020
Feb. 05, 2021
Cover [Abstract]    
Entity Registrant Name NIOCORP DEVELOPMENTS LTD  
Entity Central Index Key 0001512228  
Document Type 10-Q  
Amendment Flag false  
Entity Incorporation State Country Code A1  
Current Fiscal Year End Date --06-30  
Document Period End Date Dec. 31, 2020  
Entity File Number 000-55710  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   241,081,316
Document Fiscal Period Focus Q2  
Document Fiscal Year Focus 2021