The percentage represents the class of warrant or right Adjustment of exercise price.

No definition available.

Name:	mtal_ClassOfWarrantOrRightAdjustmentOfExercisePrice
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Class of Warrant or Right, Adjustment of Exercise Price of Warrants or Rights, Percent, Based On Market Value

+ References

No definition available.

+ Details

Name:	mtal_ClassOfWarrantOrRightAdjustmentOfExercisePriceOfWarrantsOrRightsPercentBasedOnMarketValue
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The minimum threshold period during which a written notice is required for redemption of warrants, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	mtal_ClassOfWarrantOrRightMinimumThresholdWrittenNoticePeriodForRedemptionOfWarrants
Namespace Prefix:	mtal_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Price of the entity's common stock which would be required to be attained to trigger the redemption of warrants.

+ References

No definition available.

+ Details

Name:	mtal_ClassOfWarrantOrRightRedemptionOfWarrantsOrRightsStockTriggerPrice
Namespace Prefix:	mtal_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days for stock price trigger considered for redemption of warrants.

+ References

No definition available.

+ Details

Name:	mtal_ClassOfWarrantOrRightRedemptionOfWarrantsOrRightsThresholdTradingDays
Namespace Prefix:	mtal_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Redemption price per share or per unit of warrants or rights outstanding.

+ References

No definition available.

+ Details

Name:	mtal_ClassOfWarrantOrRightRedemptionPriceOfWarrantsOrRights
Namespace Prefix:	mtal_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The "fair market value" shall mean the volume weighted average price of the common stock for the 10 trading days ending on the trading day prior to the date on which the notice of exercise is received by the warrant agent.

+ References

No definition available.

+ Details

Name:	mtal_FairMarketValuePerShare
Namespace Prefix:	mtal_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage represents the gross proceeds on total equity proceeds.

+ References

No definition available.

+ Details

Name:	mtal_GrossProceedsPercentageOnTotalEquityProceeds
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of shares in a unit.

+ References

No definition available.

+ Details

Name:	mtal_NumberOfSharesIssuedPerUnit
Namespace Prefix:	mtal_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The threshold number of specified trading period determining volume weighted average trading price , in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	mtal_NumberOfSpecifiedTradingDaysDeterminingVolumeWeightedAverageTradingPrice
Namespace Prefix:	mtal_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of warrants in a unit.

+ References

No definition available.

+ Details

Name:	mtal_NumberOfWarrantsIssuedPerUnit
Namespace Prefix:	mtal_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new units issued during the period.

+ References

No definition available.

+ Details

Name:	mtal_UnitsIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	mtal_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The issuance price of additional capital which would trigger an adjustment in the exercise price of the warrant.

+ References

No definition available.

+ Details

Name:	mtal_WarrantExercisePriceAdjustmentTrigger
Namespace Prefix:	mtal_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the warrants exercisable term from the closing of the public offering.

+ References

No definition available.

+ Details

Name:	mtal_WarrantsAndRightsOutstandingExercisableTermFromClosingOfPublicOffering
Namespace Prefix:	mtal_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The warrants exercisable term after the completion of a business combination, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	mtal_WarrantsOrRightsOutstandingExercisableTermAfterBusinessCombination
Namespace Prefix:	mtal_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21475-112644

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Face amount or stated value per share of common stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow associated with the amount received from entity's first offering of stock to the public.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

+ Details

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

- Definition

Per share or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssuedPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
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

No definition available.

+ Details

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

- Definition

Period between issuance and expiration of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_WarrantsAndRightsOutstandingTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=mtal_PublicWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=mtal_RedemptionOfWarrantPricePerShareEqualsOrExceeds18.00Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=mtal_RedemptionOfWarrantPricePerShareEqualsOrExceeds10.00Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_IPOMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_OverAllotmentOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Initial Public Offering (Details) - USD ($)			4 Months Ended
Initial Public Offering (Details) - USD ($)	Aug. 02, 2021	Oct. 31, 2020	Jun. 30, 2021
Subsidiary, Sale of Stock [Line Items]
Common shares, par value (in dollars per share)			$ 0.003
Public Warrants
Subsidiary, Sale of Stock [Line Items]
Exercise price of warrants			$ 11.50
Warrants exercisable term after the completion of a business combination			30 days
Warrants exercisable term from the closing of the public offering			12 months
Public Warrants expiration term			5 years
Issue price per share			$ 9.20
Percentage of gross proceeds on total equity proceeds			60.00%
Trading days determining volume weighted average price			20 days
Adjustment of exercise price of warrants based on market value (as a percent)			115.00%
Fair Market Value Per Share			$ 0.361
Public Warrants \| Redemption Of Warrant Price Per Share Equals Or Exceeds18.00
Subsidiary, Sale of Stock [Line Items]
Stock price trigger for redemption of public warrants			$ 18.00
Adjustment of exercise price of warrants based on market value (as a percent)			180.00%
Redemption price per public warrant (in dollars per share)			$ 0.01
Minimum threshold written notice period for redemption of public warrants			30 days
Threshold trading days for redemption of public warrants			20 days
Public Warrants \| Redemption Of Warrant Price Per Share Equals Or Exceeds10.00
Subsidiary, Sale of Stock [Line Items]
Stock price trigger for redemption of public warrants			$ 10.00
Adjustment of exercise price of warrants based on market value (as a percent)			100.00%
Redemption price per public warrant (in dollars per share)			$ 0.10
Minimum threshold written notice period for redemption of public warrants			30 days
IPO Member
Subsidiary, Sale of Stock [Line Items]
Number of units sold	25,000,000
Common shares, par value (in dollars per share)	$ 0.0001
Number of shares in a unit	1
Number of warrants in a unit	0.33
Exercise price of warrants	$ 11.50
Purchase price, per unit	$ 10.00		$ 10.00
Gross proceeds	$ 250,000,000	$ 250,000,000
Warrants exercisable term after the completion of a business combination	30 days
Warrants exercisable term from the closing of the public offering	12 months
Public Warrants expiration term	5 years
Over-allotment option
Subsidiary, Sale of Stock [Line Items]
Number of units sold	3,750,000		3,750,000