You'll fall in love with our beautiful Obsidian or Quartz fox pendants. Black obsidian is said to be thethe stone of honesty and will help to keep you on the straight and narrow. 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 with minimal crystal growth. Black obsidian is also known as Royal Agate, Xaga, Glassy Lava, and Glass Agate, it has used to make arrowheads, spear points, and other cutting tools.