The number of members appointed to the panel for arbitration.

No definition available.

Name:	msb_ArbitrationNumberOfMembersOnPanel
Namespace Prefix:	msb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of gross proceeds for royalty bonus on all tonnage shipped for sale at prices between the adjusted threshold price.

+ References

No definition available.

+ Details

Name:	msb_BonusRoyaltyGrossProceedsPercentage
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of royalty bonus of the gross proceeds of product shipped on all tonnage shipped for sale at prices between the adjusted threshold price.

+ References

No definition available.

+ Details

Name:	msb_BonusRoyaltyPercentage
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the adjusted threshold price per ton as per the collaborative agreement.

+ References

No definition available.

+ Details

Name:	msb_CollaborativeArrangementAdjustedThresholdPricePerTon
Namespace Prefix:	msb_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage for calculation of interest for litigation settlement award.

+ References

No definition available.

+ Details

Name:	msb_LitigationSettlementInterestPercentage
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of fee interest held by Mesabi Land Trust in the lands subject to the Peters Lease.

+ References

No definition available.

+ Details

Name:	msb_PercentageOfFeeInterestHeldByLandTrustInLeaseProperty
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The ceiling quantity for the first tier of base overriding royalties earned. Shipments up to this amount are subject to the first tier portion percentage in calculating the royalties earned.

+ References

No definition available.

+ Details

Name:	msb_RevenueCeilingQuantityForFirstTierOfConsideration
Namespace Prefix:	msb_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- Definition

The ceiling quantity for the second tier of base overriding royalties earned. Shipments up to this amount, above the first tier ceiling, are subject to the second tier portion percentage in calculating the royalties earned.

+ References

No definition available.

+ Details

Name:	msb_RevenueCeilingQuantityForSecondTierOfConsideration
Namespace Prefix:	msb_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage applied to the quantity shipped in the first tier, to determine the quantity on which royalties are earned.

+ References

No definition available.

+ Details

Name:	msb_RevenuePortionPercentageForFirstTierOfConsideration
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage applied to the quantity shipped in the second tier, to determine the quantity on which royalties are earned.

+ References

No definition available.

+ Details

Name:	msb_RevenuePortionPercentageForSecondTierOfConsideration
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage applied to the quantity shipped in the third tier, to determine the quantity on which royalties are earned.

+ References

No definition available.

+ Details

Name:	msb_RevenuePortionPercentageForThirdTierOfConsideration
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of revenue-generating contracts giving rise to contract asset and liability.

+ References

No definition available.

+ Details

Name:	msb_RevenueRecognitionNumberOfContracts
Namespace Prefix:	msb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The threshold quantity for the third tier of base overriding royalties earned. Shipments above this amount are subject to the third tier portion percentage in calculating the royalties earned.

+ References

No definition available.

+ Details

Name:	msb_RevenueThresholdQuantityForThirdTierOfConsideration
Namespace Prefix:	msb_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of income (loss) from royalties

+ References

No definition available.

+ Details

Name:	msb_RoyaltiesIncomeLoss
Namespace Prefix:	msb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Adjustments to the per-ton threshold price on gross revenues for royalties.

+ References

No definition available.

+ Details

Name:	msb_RoyaltyBonusesAdjustedThresholdPricePerTon
Namespace Prefix:	msb_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Definition

Price per tons for bonus royalty above adjusted threshold price.

+ References

No definition available.

+ Details

Name:	msb_RoyaltyBonusesPriceAboveAdjustedThresholdPricePerTon
Namespace Prefix:	msb_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of royalty earned on the tons shipped or deemed Shipped.

+ References

No definition available.

+ Details

Name:	msb_RoyaltyEarnedOnTonsShippedOrDeemedShippedPercentage
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

+ Details

Name:	us-gaap_AccountsReceivableNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of the asset arising from commodity contracts such as futures contracts tied to the movement of a particular commodity, which are expected to be converted into cash or otherwise disposed of within a year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(8))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_CommodityContractAssetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

+ Details

Name:	us-gaap_ContractWithCustomerAssetNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

+ Details

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

+ Details

Name:	us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

Name:	us-gaap_LitigationSettlementAmountAwardedFromOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain from litigation settlement for amount awarded from other party. Excludes claims within an insurance entity's normal claims settlement process.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483049/450-30-50-1

+ Details

Name:	us-gaap_LitigationSettlementGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Interest expense (income) directly attributable to an award in settlement of litigation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(6))
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

+ Details

Name:	us-gaap_LitigationSettlementInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-10

+ Details

Name:	us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=msb_FirstMillionTonsShippedOrDeemedShippedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=msb_SecondMillionTonsShippedOrDeemedShippedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=msb_ThirdMillionTonsShippedOrDeemedShippedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=msb_FourthMillionTonsShippedOrDeemedShippedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=msb_BeyondFourMillionTonsShippedOrDeemedShippedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ContractWithCustomerBasisOfPricingAxis=msb_RoyaltiesBasedOnProductShippedBaseAmountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ContractWithCustomerBasisOfPricingAxis=msb_RoyaltiesBasedOnProductShippedBonusAmountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ContractWithCustomerBasisOfPricingAxis=msb_RoyaltiesBasedOnRawMaterialsMinedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue (Details)			1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 04, 2024 USD ($)	Sep. 06, 2024 USD ($)	Mar. 31, 2024 item	Apr. 30, 2025 USD ($) contract MT $ / T shares	Apr. 30, 2024 USD ($) shares	Jan. 31, 2025 USD ($) $ / T	Jan. 31, 2024 $ / T
Disaggregation of Revenue [Line Items]
Number of units outstanding \| shares				13,120,010	13,120,010
Revenue from Contract with Customer [Abstract]
Royalty income (loss)				$ 4,349,472	$ 6,010,608
Base overriding royalties, first tier portion percentage				90.00%
Base overriding royalties, first tier shipment ceiling (in million tons) \| MT				4
Base overriding royalties, second tier portion percentage				85.00%
Base overriding royalties, second tier shipment ceiling (in million tons) \| MT				2
Base overriding royalties, third tier portion percentage				25.00%
Base overriding royalties, third tier shipment threshold (in million tons) \| MT				6
Litigation settlement, damages	$ 71,185,029
Accrued income receivable				$ 1,916,756		$ 1,160,761
Bonus royalty percentage				0.50%
Bonus royalty, gross proceeds percentage				3.00%
Royalty bonuses, price above adjusted threshold price per ton \| $ / T				2
Adjusted threshold price (in dollars per ton) \| $ / T						69.41	67.75
Number of members on panel for arbitration \| item			3
Litigation settlement, amount		$ 59,799,977
Litigation settlement, interest		$ 11,385,052
Litigation settlement, percentage		10.00%
Litigation Settlement, Gain	$ 71,185,029
Percentage of fee interest owned by Mesabi Land Trust in the lands subject to the Peters Lease				20.00%
Number of customer contracts \| contract				1
Net contract asset				$ 1,179,208		$ 240,642
Contract asset				1,179,208		240,642
Contract liability				$ 0		$ 0
Minimum
Revenue from Contract with Customer [Abstract]
Bonus royalty, gross proceeds percentage				1.00%
Royalty bonuses, adjusted threshold price \| $ / T				10
First Million Tons Shipped or Deemed Shipped [Member]
Revenue from Contract with Customer [Abstract]
Royalty earned on tons shipped or deemed shipped, percentage				2.50%
Second Million Tons Shipped or Deemed Shipped [Member]
Revenue from Contract with Customer [Abstract]
Royalty earned on tons shipped or deemed shipped, percentage				3.50%
Third Million Tons Shipped or Deemed Shipped [Member]
Revenue from Contract with Customer [Abstract]
Royalty earned on tons shipped or deemed shipped, percentage				5.00%
Fourth Million Tons Shipped or Deemed Shipped [Member
Revenue from Contract with Customer [Abstract]
Royalty earned on tons shipped or deemed shipped, percentage				5.50%
Beyond Four Million Tons Shipped or Deemed Shipped [Member]
Revenue from Contract with Customer [Abstract]
Royalty earned on tons shipped or deemed shipped, percentage				6.00%
Base Overriding Royalties
Revenue from Contract with Customer [Abstract]
Royalty income (loss)				$ 2,425,094	3,417,645
Bonus Royalties
Revenue from Contract with Customer [Abstract]
Royalty income (loss)				1,783,835	2,450,133
Fee Royalties
Revenue from Contract with Customer [Abstract]
Royalty income (loss)				$ 140,543	$ 142,830