Opal is a hydrated amorphous form of silica with a 3 to 21% water content. Because of its amorphous character (meaning it has no crystalline structure), it is classed as a mineraloid rather than a mineral. It is deposited at a relatively low temperature in the fissures of almost any kind of rock. Its internal structure makes it diffract light. Opal has a hardness of 5-6.5 on Mohs scale and it is widely used in jewelry making mostly cut and polished to form a cabochon.The Romans believed opal to be the most powerful stone of all, carrying in it all the colors of other precious gems. The Bedouins believed to be fallen from the sky during thunderstorms and that it contains lightning.
Opal has three basic types: precious opal, common opal and fire opal.
The precious opal is the rarest, known as “rainbow opal”. It produces beautiful play of color, brilliant flashes or streaks of iridescent color when turned in the light. The “common opal” has usually a milky or pearly luster, it does not exhibits play of color. The “fire opal” is transparent to translucent. Its color is vivid red, orange or yellow. This stone has no play of color either, but occasionally can show bright green flashes.
It is a stone of inspiration and change enhancing ones creativity and imagination. It can be used to avoid nightmares, to calm turbulent emotions, to enhance self-esteem and self-worth. It is said to be stone of love intensifying what one is feeling and releasing inhibitions.
On a physical level opal is believed to purify the blood and kidneys and regulate he insulin production. It helps reduce fever and stimulates memory. It is also beneficial for the health of the eyes.
It stimulates the Hearth and the Crown Chakra, (but since it occurs in nearly all colors, the dominant color energies stimulate the corresponding chakras).
Opal is the national stone of Australia, and birthstone for the month of October.