The Holy Grail?
Maybe it's wooden.
Speculated because Jesus was a carpenter so his cup may have been made of wood.
Maybe it's golden.
Because of the belief of heavenly wealth.
It could be made out of greenish glass.
The Santo Calion was a greenish glass chalice believed to be the Grail in the Medieval era.
Most likely it has not that much mass.
It's a cup, so it's small.
Some think it is already found,
Some believe it's in a reliquary in a church around the world somewhere.
Most think it could still be somewhere around.
Most believe it is still missing.
Hidden at some scary place,
Just like in Indiana Jones and the Last Crusade.
In some ancient buildings base.
Where it was hidden in an ancient building.
It is a mystical ancient object.
It is the Cup of Christ.
It's believed to have a great effect.
The power of everlasting life.
It's part of stories often told.
In the Bible, in Arthurian legend, in Monty Python, etc.
It's more than one millennium old.
It's 2 millennia old.
It occurs in middle age lore.
As part of Arthurian legend.
It was often searched for.
And was searched for extensively by treasure hunters.