Opal is a gemstone, but it is not classified as a mineral. Rather it is a mineraloid, meaning that it does not have any crystalline properties.
Physical Properties of Opal
Opal is composed of silica with water content. On average, the water content ranges from 6-10%, but it may be as high as 21% of the weight of the stone. Opal is an incredibly recognizable stone, owing to its light-refracting properties.
Opals have an iridescent sheen, and the colors they display shift as your perspective changes. Opals may be white, grey, red, orange, yellow, green, blue, pink, olive, black, and brown.
These are their dominant hues only each one of those opals may contain a myriad different colors owing to their refractive properties. An opal can contain any color in the rainbow.
Almost all the world’s opals are mined in Australia. The continent is responsible for 97% of the world’s opal supply. Ninety percent of those opals are white and crystal opals. Other colors of opal are much less common, with black opal and boulder opal being quite rare.
Opals can also be created synthetically in a lab, but can easily be told apart from natural opals because the synthesis of opals in a lab creates a regular pattern which can be seen under a microscope.
List of Gemstone Meanings: For our full list of gemstone meanings.
History of Opal
Historians debate where the word ‘opal’ came from. Opal may derive its name from the Roman word ‘opalus’, but it could also come from the Sanskrit ‘upala’ or the Greek ‘opillos’. Pliny the Elder has also reference opals, and it has been suggested that the name was derived from Ops, the wife of Saturn.
Opal was associated with good luck in Medieval times because of the rainbow of hues. Those hues were associated with different gemstones, and thus with the different beneficial properties attributed to each of them. An opal carried the luck of many different gemstones.
It was also believed that if the stone were wrapped in a fresh bay leaf, it would confer invisibility (strange that such a belief could persist after being tested). Amusingly enough, the reputation of opals took a turn for the worse when Sir Walter Scott published a novel called Anne of Geierstein in 1829. In the book, opals were associated with death and bad luck. After he published, opal sales in Europe dropped by 50%.
Metaphysical Properties of Opal
Opal is the birthstone for October. It is associated with true love, confidence, happiness, and loyalty, despite the fact that it is also associated with water, and thus with mutability. Opals are generally believed to be extremely lucky, a belief which has persisted far longer than the 19th century superstition that opals are unlucky.
Different meanings are associated with different colors of opal. In folk remedies, they are used to stimulate the glands and improve metabolism. In Feng Shui, placed in the northern direction, opal may be associated with harmony and spirit.