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v3.25.2

MINERAL PROPERTIES (Details Narrative) $ in Thousands | 12 Months Ended
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Jun. 30, 2025 USD ($)
Extractive Industries [Abstract] |
Exploration expense for OTP extension payments | $ 310
Future Option to Purchase Extension Payment Obligations | $ 93

X
- Definition The element represents exploration expense for o t p extension payments. + References No definition available. + Details
Name: | niobf_ExplorationExpenseForOTPExtensionPayments
Namespace Prefix: | niobf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The element represents future option to purchase extension payment obligations. + References No definition available. + Details
Name: | niobf_FutureOptionToPurchaseExtensionPaymentObligations
Namespace Prefix: | niobf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | srt_ExtractiveIndustriesAbstract
Namespace Prefix: | srt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration