Black Obsidian is associated with the first chakra. This energy center pertains to the earth, the physical, to survival and to the personal ego fulfillment.
Black Obsidian should only be used when one is educated about its powers and prepared to process the changes that this stone often relentlessly puts one through.
Ruled by the planet Pluto, Black Obsidian’s purpose is to take the mind through the darkened areas of the subconscious to establish identity in the superconscious. Being a Plutonian teacher, Black Obsidian does not cater to the ego. Instead, it bluntly and often tactlessly shows the ego-self where it is at and what it needs to change in order to advance to the next step of evolution. It acts as a mirror that reflects the flaws in one’s nature and magnifies the fears, insecurities and egocentric attitudes that suppress the soul’s superior qualities.
Source: Crystal Enlightenment by Katrina Raphaell