Okay.. what exactly is this pictured below? digging a pool, I hit this pocket of black sand/small round pieces of stone and hundreds/thousands of these marble sized stones. the pocket was about 1 1/2-2 ft dia. and started about the middle of the 16 ft wide hole and continued under the side. this was about 6 ft deep. the mix has a petroleum smell to it. digging holes for over 20 years, this is the first I've seen this. I do find clay marble sized objects in the right type of sandy clay, but these are stone/rock. Now this is deep in the swamp buried in blackjack slimy mud. there are no rocks, no stones... nothing but mud in this part of the world. the only rocks you'll find were trucked or barged in.. nothing naturally occuring, except the ones in my head of course. I saved some samples and am curious to find exactly what this is.
