The amount of interest and other costs that an entity incurs in connection with the borrowing of funds that are directly attributable to the acquisition, construction or production of a qualifying asset and which form part of the cost of that asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 23
-IssueDate 2024-01-01
-Paragraph 26
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=23&code=ifrs-tx-2024-en-r&anchor=para_26_a&doctype=Standard
-URIDate 2024-03-27

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Balance Type:	na
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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

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- Definition

Amount of loss caused due to demolition.

+ References

No definition available.

+ Details

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Namespace Prefix:	nmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the percentage of NSR on property.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of royalty buy back right.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of royalty buy back right exercised.

+ References

No definition available.

+ Details

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- Definition

Represents the price of royalty buy back right.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Represents the price of tranche to be purchased.

+ References

No definition available.

+ Details

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Namespace Prefix:	nmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Percentage of net smelter royalty after exercising buyback option.

+ References

No definition available.

+ Details

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- Details

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PROPERTY, PLANT AND EQUIPMENT- Additional Information (Details) - CAD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Aug. 28, 2020	Aug. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Property and equipment
Amount of borrowing costs			$ 2,079	$ 825
Percentage of royalty buy back right, exercised		1.00%
Percentage of royalty buy back right	3.00%	3.00%	2.00%
Price of royalty buy back right	$ 4,306	$ 1,869
Percentage of NSR		0.20%
Amount of purchase price of tranche		$ 200
Remaining NSR percentage		2.00%
Demolition loss		$ 1,098
Mine under construction
Property and equipment
Amount of borrowing costs			$ 2,079	$ 825
Price of royalty buy back right		963
Becancour Battery Material Plant under construction
Property and equipment
Price of royalty buy back right		$ 906