Subsequent Events - Silver Purchase Agreement, Silver Stream Equity Subscription, Redemptions Backstop Facility (Details)	Mar. 20, 2023 USD ($) oz
Subsequent Event
Period of achievement	10 days
Subsequent Event [Member]
Subsequent Event
Upfront cash deposit	$ 75,000,000
Increase in upfront cash deposit	$ 15,000,000
Percent of payable silver	100.00%
Percent of produced silver at the CSA Mine	90.00%
Ounce to be quoted on silver price \| oz	25.50
Percent of refined silver price for each ounce	4.00%
ROFR term	7 years
Percentage of issued share capital in ROFR	5.00%

Amount of increase in upfront cash deposit to be entitled in the silver commodities.

No definition available.

Name:	mtal_PhysicalCommoditiesSilverIncreaseInUpfrontCashDepositToBeEntitledOnSilverProduction
Namespace Prefix:	mtal_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Indicates the ounce quoted on silver market price.

+ References

No definition available.

+ Details

Name:	mtal_PhysicalCommoditiesSilverOunceQuotedOnSilverMarketPrice
Namespace Prefix:	mtal_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- Definition

Percent of produced silver to be equal to Purchaser in the silver commodities.

+ References

No definition available.

+ Details

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

- Definition

Percent of produced silver to be transferred to Purchaser in the silver commodities.

+ References

No definition available.

+ Details

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

- Definition

Indicates the percent of silver reference price on each ounce.

+ References

No definition available.

+ Details

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

- Definition

Indicates the percent of issued share capital ceases to be hold.

+ References

No definition available.

+ Details

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

- Definition

Term of ROFR.

+ References

No definition available.

+ Details

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

- Definition

Represents the threshold period required to achieve the trigger price in the silver commodity.

+ References

No definition available.

+ Details

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

- Definition

Amount of upfront cash deposit to be entitled in the silver commodities.

+ References

No definition available.

+ Details

Name:	mtal_PhysicalCommoditiesSilverUpfrontCashDepositToBeEntitledOnSilverProduction
Namespace Prefix:	mtal_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: