While Obsidian is ~70% silicon dioxide, darker specimens and very black pieces are certain to contain ferromagnesian impurities. Basically not all that great either.
I'd be inclined not to use either.
All is well here this morning, and night.. fish seem much happer and I will be doing another WC very soon..
In regards to the newage stuff, I have a few books for my aquarium habits from a new age author named Melody - lots of good info in there. I used to collect rocks and such as a kid and it kinda grew on to my adult hood. Sticking them in my tanks is one way to display them so that they dont have to sit in boxes
In reagards to the obsidian, it is snowflake obsidian which is pitch black with white spots... its not like the clear glassy obsidian that usually is thought to be smoky quartz..
My luck to pick 2 completely different stones and come out with the same problem in both tanks...