Obsidian is a stone of protection and grounding. Formed from rapidly cooled lava. Obsidian is often worn to shield your energy in situations where you know you may feel overwhelmed with other peoples energies or presences. Such as public places.
Avoid wearing obsidian in places you want to be social because it will then be shielding your energy when trying to connect with others.
Obsidian is water safe and it’s placement is on or near the root chakra. It can even be used to ground yourself during meditation by holding it in your hands.