Instead of linking to a bank account denominated in sterling or another traditional currency, these new cards are tied to accounts where wealth is measured in bitcoins and physical gold.
London Block Exchange's Dragoncard is the bitcoin-backed card provisionally authorised by the Financial Conduct Authority and scheduled to be offered within weeks.
Glint works in a similar way but the cardholder's account is stocked with physical gold.
The gold is purchased on behalf of the cardholder by Glint and stored in a Swiss vault. Like other, existing gold investment services, each account holder's entitlement to their share of physical gold is independently audited.
The account is managed via a smartphone app. The account holder can use the app to select payments either in gold or in sterling (and other currencies are being rolled out in future months).
The Glint card uses MasterCard as its payment processor, so can be used anywhere that accepts MasterCard. The Dragoncard will use Visa.
Once the payment is made, a Glint cardholder's account will show a deduction either in sterling or by weight in gold - depending on how the cardholder has configured their account.