Opals

“The type of opal found in the [Martian] meteorite [Nakhla] is known as ‘fire opal’ because of its vivid orange, yellow, and red colours. This type of [opal] often forms in and around hot springs where microbial life thrives. It is possible that opals on Mars could have trapped microbes and [therefore] reveal valuable information about life on Mars. Fire opal is rare and on Earth the most significant deposits are in Mexico. In Australia, fire opal is only mined at one remote location near White Cliffs, Western Australia,”

-Opals by South Australian Museum