Opals are formed from centuries upon centuries of seasonal rains that leach microscopic silica particles from sandstone, carrying them deep into underground fissures and cavities. As the deposited materials dry, the microscopic silica spheres become compressed into a closely-packed lattice. As light travels through this microstructure, it creates a dazzling kaleidoscope of flashing rainbow colours, called play-of-colour. Australian opal is best-known and the country remains the most prolific source of opals – mainly white and black. Ethiopia is the newest source, with the first discovery in 1994. The most prolific source was in found 2008 mostly white opal, that was formed from the silica from ancient volcanic ash. Ethiopian opal is believed to be an emotional intensifier, enhancing the true nature of those who wear it. Some say it strengthens the will to live and shields the wearer against negativity, burning off karma. Opal from this area occurs in a wide range of body colours. Much of the opal has a brown, red, or orange body colour; however, yellow, white, and clear body colours are also found. Ethiopian Opal is birthstone for october.