The name opal is thought to be derived from the Sanskrit upala, meaning “precious stone,” and later the Greek derivative “Opallios,” meaning “to see a change of color.” Opal displays an array of very brilliant miniature rainbow iridescent effects, all mixed together.The more brilliant the color, or fire, the more valuable the gem. Opals are mostly found in Australia, Mexico, the USA, South America, Britain, Canada, Brazil, Czech Republic and Slovakia.