Obsidian is one of the more difficult to locate resources in Ark, and is used in advanced crafting. Found for the most part in the higher mountains, this resource is best harvested with the Metal Pick or Dino Power. Keep in mind that this resource is most plentiful up in the mountains, though not all mountains feature Obsidian.
Harvesting Obsidian can be a challenge.The journey to where the Obsidian is found can often be quite dangerous. Of course, in many cases it's not exactly safe on the mountain tops either.
There are dangerous Dinos that spawn near the mountain tops, and freezing cold nights can seriously injure or even kill you. Of course, this varies in degrees, depending on the region in which you are harvesting.
There are two ways to harvest Obsidian effectively: with a Metal Pick or an Ankylosaurus. Either way works well, but the Anylo is faster and can carry a lot.