Obsidian

Obsidian is highly regarded for its ability to provide protection, grounding, and shielding against negative energies. Obsidian is also associated with enhancing self-awareness, promoting emotional healing, and assisting in spiritual growth. Its sharp and transformative energy is believed to aid in releasing blockages, facilitating personal insight, and fostering inner strength.
Obsidian is volcanic glass formed when Lava runs into Water. It comes in different colors due to impurities and mineral inclusions during its formation.  It is rock, not a crystal,  but has been considered a gemstone.