Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly without crystal growth. Pure obsidian is usually dark in appearance though the colour varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black colour.
Black Obsidian will help to clean and remove negative energies in a sacred space or environment. It also assists in releasing those emotions reactions that cause negative energy such as anger, jealousy, greed, resentment.
As these ar natural pieces, they will vary in colour, size and shape.