Unlike most other gemstones, the opal is non-crystalline and is formed from  hardened silica gel. It is known for its rainbow iridescence. The name "opal" is thought to be derived from the Sanskrit upala, meaning "precious stone." the opals used in ancient times came from the former Czechoslovakia, but today, most are mined in Australia.

In Asia, the stone is viewed as a symbol of home and prosperity.