Obsidian is a result of volcanic molten lava cooling so fast it did not have time to crystalize, so it is a form of natural glass. Thus, energetically it works very quickly and powerfully. Like a mirror, nothing can be hidden, so all is revealed including things one might not want to look at. As such it is a force for catharsis and growth by promoting compassion & strength. At the same time, Obsidian provides protection, grounding, and calming effects to heal from trauma, especially for sensitive people. It repels negativity and channels power into good.
Tumbled stones are smaller pieces of crystals or rocks that have been processed in a rock tumbler with water, sand, and grit. Over weeks in a tumbler, the stone edges and surfaces become smooth and sometimes highly polished to bring out the beauty of the stone. The pleasing shape and size of tumbled stones make them desirable as more inexpensive and usable crystals.