The interest rate on borrowings. [Refer: Borrowings]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_7&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_BorrowingsInterestRate
Namespace Prefix:	ifrs-full_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of financial assets classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2023-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_55&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_DerivativeFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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.

+ Details

Name:	ifrs-full_DisclosureOfDetailedInformationAboutBorrowingsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of liabilities that are: (a) a contractual obligation: (i) to deliver cash or another financial asset to another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially unfavourable to the entity; or (b) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to deliver a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose, rights, options or warrants to acquire a fixed number of the entity’s own equity instruments for a fixed amount of any currency are equity instruments if the entity offers the rights, options or warrants pro rata to all of its existing owners of the same class of its own non-derivative equity instruments. Also, for those purposes the entity’s own equity instruments do not include puttable financial instruments that are classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. As an exception, an instrument that meets the definition of a financial liability is classified as an equity instrument if it has all the features and meets the conditions in paragraphs 16A-16B or paragraphs 16C-16D of IAS 32. [Refer: Financial instruments, class [member]; Financial assets; Derivatives [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 25
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_25&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_FinancialLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum amount of funding available to the company under the borrowings.

+ References

No definition available.

+ Details

Name:	mtal_BorrowingsMaximumFundingAvailable
Namespace Prefix:	mtal_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Threshold amount of outstanding balance under the borrowings, up to which the difference between the product's Market Price and the product's Cash Price will be credited .

+ References

No definition available.

+ Details

Name:	mtal_BorrowingsThresholdOutstandingBalanceUpToWhichCreditOfDifferenceBetweenProductsMarketPriceAndProductsCashPriceWillBeMade
Namespace Prefix:	mtal_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Cash payments receivable by the company for one tonne of refined copper delivered, represented as a percentage of Copper Market Price.

+ References

No definition available.

+ Details

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

- Definition

Amount of deliveries made by the company as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	mtal_DeliveriesMade
Namespace Prefix:	mtal_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of produced copper payable by the company.

+ References

No definition available.

+ Details

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

- Details

Name:	ifrs-full_BorrowingsByNameAxis=mtal_CopperPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans and borrowings - Terms and conditions of Copper Purchase Agreement (Details) - USD ($) $ in Thousands	Jun. 16, 2023	Jun. 30, 2023	Dec. 31, 2022	Jan. 01, 2022
Loans and borrowings
Financial liability		$ 809,219	$ 290,151	$ 262,574
Fair value of compound embedded derivative		9,219
Copper Purchase Agreement
Loans and borrowings
Available Copper Deposit	$ 75,000
Produced copper payable (as a percent)	96.20%
Deliveries made towards the Copper Stream		0
Copper Cash Price receivable for one tonne of refined copper delivered (as a percent)	4.00%
Threshold amount of Copper Deposit up to which the difference between the Copper Market Price and the Copper Cash Price will be credited	$ 0
Financial liability	79,430
Fair value of compound embedded derivative	$ 4,430	$ 5,479
Effective interest rate (as a percent)	13.12%