Fake stone for Excalibur - King Arthur story

[joeranger]

On Friday, I am appearing as King Arthur at a kids Diabetes camp.
I would like to make a fake stone to pull Excalibur from. It would be really cool if I could figure out a way to make it so that only I could pull the sword. (latch, magnet...)

I could also buy one of those fake rocks they use to cover backyard well heads.
Has anyone made fake rocks?

 

[LTsmash1200]

I made this stone pedestal for my holy grail. It's just foam covered in spackle. While it was semi dry I patted it all over with plastic grocery bags to give it more of a stone look, next I sprayed it with one of those stone texture spray paints to give it some grainyness. Then I painted a base of terra cotta color, followed by several shades of browns and black dry brushed on, then a wash of brown/black, then I flicked specks of the black wash on with the brush and left it sit to make the little dots.

I watched a bunch of fake stone videos on youtube and took some techniques from several of them. You could do the same with any shaped foam really and then just use probably a light gray as your base.