Obsidian
 
Sagittarius Scorpio
 
Obsidian is said to be extremely protective and helps immensely with Shadow work/self reflection.
Obsidian is often associated with mystery and has a very strong ability to absorb. For this reason it is used often in feng shui, spiritual connection and protection. It is also known as a spiritual cleanser because of its ability to absorb psychic smog and help to see things more clearly.