THEY were created to mark the dawn of Christianity in Scotland and have stood in silent witness to the religion's growth for almost 1500 years.

Now the significance of the carved stones of Iona Abbey to the wider medieval world is to be investigated by a panel of international experts who will gather in Scotland this year.

Historians, archaeologists and members of the Iona Community will meet on the Inner Hebridean island in April to carry out a fresh examination of many of the ancient abbey's carvings.

The work is part of the preparations for the 1450th anniversary of St Columba's arrival in Scotland which takes place in 2013. It will hopefully shed new light on the origins of the carvings as well as their place in the development of Christianity through the ages.

St Columba, an Irish monk, is believed to have brought Christianity to Scotland.

He established the first abbey on Iona in 563 AD and got a foothold for the religion by converting leaders of the Pictish tribes in the area.

Included among the abbey's collection are stone crosses dated to within 200 years of the abbey's founding, some of which show Celtic influences thought to come from Ireland. Others bear the stamp of the Vikings who first raided Iona in 794 AD.

Experts in stone carving from Norway will be among those who examine the carvings, the first time they have been studied by experts in ancient Scandinavian culture.

A spokeswoman for Historic Scotland, which is organising the workshop, said being able to examine the stones in situ adds an extra dimension to what can be learned.

She added: "The scale and quality of the collection is what makes it so important. It is the largest collection of early- medieval sculpture in Scotland and the stones are still in the place with which they were originally associated.

"Many stones of this type get moved off site, to museums and the like. While this has a definite place in conservation of such sculptures, it does mean that something of the cultural significance of the sculptures is lost.

"These things were meant to be seen and understood in their contexts. By maintaining the connection with their original site there is more potential for gaining understanding of their use and meaning in their time as well as ours."

The carved stones include St John's Cross and St Oran's Cross, both dating from the eighth century, and a cross slab created 100 years later. The crosses are thought to be among the finest examples of such sculpture to survive.

Later medieval sculptures found in the abbey's collection include some well-preserved west Highland grave slabs, which indicate the continued importance of Iona into the medieval period when it was under the influence of the Lords of the Isles.

New information learned from the workshop will be put on display in 2013 as part of the anniversary celebrations.

Fiona Hyslop, Cabinet Secretary for Culture and External Affairs, said: "Iona Abbey is Scotland's best-known place of pilgrimage, a springboard for Christianity in northern Britain, and reputed burial place of the early kings of Scotland.

"Its mystical atmosphere and beautiful carved stone collection draws people back time and again, and for all sorts of reasons.

"We know that the abbey and the carved stones of the Iona School are hugely significant in Scotland's history.

"As we look at how we might mark the 1450th anniversary of Columba's arrival in 563, it is well-timed that experts and interested parties will soon come together to evaluate what we know about this spiritual island, and what more we can still learn."