Opal is a mineraloid, a material that lacks a crystal structure but has a regular composition.  It may be created by the minerals cristobalite and tridymite or amorphous silica.  It is commonly divided into precious opal, which displays a play of color, and common opal.

Black Opal is said to reduce anxiety and worry and also helps to overcome fears by assisting in breaking down limiting beliefs. Helps to provide confidence in breaking down barriers that have held you back. Helps reduce negativity in the environment and from others. The Black Opal stone is a strong stone that can allow you to take a stand and help you achieve the goals that you have set up for yourself.