And how large was the stone?

The gospels do not give us the precise measurements. BUT the Greek language states the stone was

 LARGE 

EXTREMELY

Mark 16:4. Interlinear

Mark 16:4,And when they looked, they saw that the stone was rolled away: for it was very great.
Although no one has seen the Great Stone for 1000's of years, we can see today that the stone was 15'' thick by the lighter colour in the channel where the stone rolled.

So where is this stone today?
This original stone has never been found or been seen for 1000's of years. If we could find this stone it can only prove one thing, that this is the true tomb that was owned by Joseph of Arimathea.