Hardness 5.5-6.5, Specific gravity 2-2.25, Refractive index 1.44-1.47

Opal is hydrated amorphous silica. Opals are used as birthstones. They are said to be good for those born in October.

Opals with variable color changes and that are bright, have a good value. Black opal is rare, and is usually the most valuable. Most good quality opals are found in Australia, although they are generally processed in Asia. Opals are also found in Indonesia.

Opals refract light and then reflect it in a play of colors. Opals can be found in a wide selection of colors and patterns. Water is the main ingredient of opals, so do not allow them to dry out. Opals are easily scratched, especially when set in a ring. They can also be easily shattered either by hitting them or a rapid change in temperature.

Opals help with spiritual and religious life, finances, family life, and they improve one's beauty. They help develop the ability to foretell the future, and many astrologers use them for this purpose. They can also help with legal cases.With use, opals become dull. After some time, they should be replaced.