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The change in the fair value of the Contingent Consent Warrants is presented below: (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Jun. 30, 2024 | Jun. 30, 2023
Debt Disclosure [Abstract] |  |
Initial valuation, at beginning | $ 1,710 | $ 1,221
Change in valuation | 655 | 489
Valuation, at ending | $ 2,365 | $ 1,710

X
- Definition The element represents change in valuation of warrants. + References No definition available. + Details
Name: | niobf_ChangeInValuationOfWarrants
Namespace Prefix: | niobf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

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- Definition Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price. + References No definition available. + Details
Name: | us-gaap_WarrantsAndRightsOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant