Rainbow obsidian shows rainbow layers within its blackness when placed under a light source. These rainbows may show the full spectrum or show just part of the colour range. The rainbow colours occur due to inclusions, often minute gas or water bubbles, that were trapped during the obsidian's solidification process. This stone is of great use to anyone working deeply on self-healing, or who is willing to undertake the work necessary to reconcile their shadow aspects in order to grow spiritually. The polished surface acts like a "mirror for the soul", not only revealing us in stark honesty, but also showing the beauty that is deep within all of us. Not a stone for the fainthearted perhaps, but HUGELY beneficial for those who have the courage and honesty to work with it.