I've yet to figure out how to post images on here... The thumbnails are too small, and the URL's are only slightly larger...
But yes, the larger stone seems to be many, many smaller stones tightly compacted together. It was solid and dense when I cut through it though; it didn't crumble apart.
The ones on the top right of the first photo, especially, were smooth, solid globs, like marbles. Definitely not a compilation of smaller stones.