is obsidian formed underground
The best obsidian is formed underground near a volcanic vent because those rocks will have limited impurities. Obsidian flows are so slow that often other obsidian flows will occur on top of each other causing a streaked appearance in the obsidian rock.he result is a rock that cooled so fast, crystals did not get a chance to form. Obsidian is a volcanic glass with a smooth and uniform structure. Interesting Obsidian Rock Facts: Different varieties of obsidian rock get their names from their appearance.