by 32012323 » Thu Mar 11, 2010 9:17 am
Adjacent tiles it does from what I've seen, so it might be safe to assume any other clay tiles in the node are going to degrade also.
I've dug up QL 13 clay to find by the second to third trip all tiles in the node have decreased to QL 11 until some game time has passed.
Somebody else might have a more detailed perspective on it, just vocalizing what I've witnessed so far.
Hope it helps.