Our lettuce sprouts are in jiffy pots and the soil and pots are moldy. Can plants be saved?
I used to live in Virginia, so I'll hazard a guess. Keep in mind, the geology varies quite a bit there. Shiny black pieces that look like obsidian? Do you see a lot of 60 or 120 degree angles along the edges? Could be an amphibole (like hornblende) rather than obsidian. The not-gold, if it is flaky, may be a weathered mica (muscovite, or even biotite). Perhaps you're seeing the remnants of a schist or gneiss that has been weathered and eroded for millions of years, particularly if you're southeast of the Blue Ridge.
It sounds you possibly have vermiculite. It might be a natural occurrence or it might be imported/purchased, its a great soil for gardening/growing stuff. The shiny black, gold and green are all weathered biotite. Of course not being able to see/hold means this is just a guess. And a little bit of internet digging (haha pun) shows that there is at least one company that mines it in Virginia. One company, Virginia Vermiculite LLC, produces vermiculite in Virginia. The company operates an open pit mine near Trevilians, in Louisa County. This is one of only three active vermiculite mines in the United States (Potter, 2003). The deposit is in an 80- to 100-foot thick weathered zone in mafic rocks of the Green Springs pluton.
