I couldn't find a 24" stone anywhere. I haven't seen very many 24" stones though are you sure that is the correct size?
About 90% sure on the size, yes. Some of them were (I think) as large as 2' x 3'.
A friend of Sacha's is having an in-ground pool demolished; the deck surrounding the pool is made up of these things and we can have as many as we like so long as we remove them before the wrecking crew gets there.
We've moved about 16 of the bigger ones so far, and roughly 30 of the smaller stones. Most of 'em are warped like you mentioned Aaron, but not so badly that they won't work for our purposes.
Did a little research and please forgive my math but as I figure it a 12" x 12" stone weighs 22 lbs, quadruple the size and you come up with 88lbs.
Someone else told me that a 70lb bag of cement will fill a 2'x2'x2" mold with a bit left over. Not sure I want to risk me plus one of these suckers against the sturdiness of our bathroom scale...
70-90lbs each would explain a few things, though.
11 of the larger stones in the little trailer made for warm wheel bearings, and a full-size truck with the box about half full of the things felt like it wanted to do a wheelie every time we hit a decent bump.
Goin' back for another 1/2 truckload tonight... good exercise.