Archbishop of Wales, Andrew John, takes part in a ceremony to bless The Cross of Wales at Holy Trinity Church in Llandudno, north Wales, on April 19, 2023. AFP
Pope Francis gave the two fragments of the "True Cross", one 5 millimetres long and the other 1 centimetre, as a gift to mark the crowning of the monarch and his wife Camilla as queen on May 6.
They have been fashioned into a tiny cross and incorporated into the overall design, visible behind a rose crystal gemstone.
The Archbishop of Wales, Andrew John, blessed the new Cross of Wales before dignitaries and parishioners at a service in Llandudno, north Wales.
It will now be taken to London and be carried at the head of the coronation procession.
The archbishop said the cross "speaks to our Christian faith, our heritage, our resources and our commitment to sustainability".
"We are delighted too that its first use will be to guide Their Majesties (Charles and Camilla) into Westminster Abbey at the coronation service."
Charles presented the Cross of Wales to the Anglican Church in Wales to mark its centenary.
It took designer Michael Lloyd two years to make and was crafted from recycled silver bullion, with fragments of Welsh timber and slate.
After the coronation, it will be shared by the Anglican and Roman Catholic churches in Wales.
Charles applied the king's mark of authentication, a leopard's head, to the silver elements of the cross during a visit to The Goldsmiths' Centre in London last year.