The Holy Grail hype originated in the middle ages, more than 1000 years after the crucification. The idea of the grail is linked with the King Arthur sage. The earliest sources either give no description of its outward appearance or describe it as a stone.
Later came the notion of the grail being a cup. According to Christian legend it was a cup used at the last supper or to catch some of Jesus' blood during the crucification by Joseph of Arimathea. This Christian grail tradition originated no earlier than AD 850.
The story of the grail is a legend rooted in the realm of myths. It is interesting for those who investigate how myths appear, change, and disappear. For people trying to find real objects it is irrelevant.
(C) 2006-2011 Thorsten Straub, www.biblical-finds.com