Visitors are being urged to stop leaving coins in cracks at the Giant's Causeway in Northern Ireland to prevent damage to the stones at the world-famous tourist site. Thousands of coins have been wedged into joints by tourists in the past decades "as a token of their love or luck" says Cliff Henry, the site's Nature Engagement Officer. However, the coins rapidly corrode and expand, causing the rock to flake and leaving rust coloured streaks, Henry tells AFP. "Once some visitors see other people have done it, they feel that they need to add to it, but we are actively discouraging that," says Joan, one of the Giant's Causeway tour guides tasked with tackling the problem. IMAGES AND SOUNDBITES