Fire opal is also fairly transparent, but its background color may be yellow, orange, red or brown. Sometimes it doesn't even have the typical play of color. It's often called Mexican opal because Mexico is a major source of this type. Fire opal with a red body color is also known as cherry-v opal. Opal that is colorless, transparent to semitransparent and has little or no play of color is called jelly or water opal.
Opal quality is judged by the number of colors exhibited and the evenness of the pattern.
GIFT Australia is the world's most important source of opal. The opal miner is a strange breed of individual. He chooses to lead a spartan life in a particularly barren and dry corner of the world while he searches for his rainbows. To escape the extreme temperatures, he must burrow a home underground. Opals are usually found in sandstone or claystone.