The name opal is adapted from the word opalus, Latin for ‘gem’. The uniqueness of gem-quality opals lies in their extensive play of colour, the details on the opals appearing to assume different hues when viewed from different vantage points.
Gem-quality opals are made up of spherical silicon dioxide molecules tightly packed and stacked together in layers.
The colours produced by opals depend on the thickness of these layers and the diffraction of light on them. Compared to blue and green hues, opals with red hues are rarer, due in part to their molecular arrangement.
Opals with a milky white body colour and translucent or pastel iridescence are known as White Opals, while Black Opals exhibit an Aurora-like iridescence against a black body colour. Both these opals are mined in Australia.
Other opals such as the Water Opal boast of a clear transparent body colour, while the Fire Opal shows off a red body colour. These are mined in Mexico. In water, these gems dazzle with the opalescence of rainbow colours.
Due to its high water content, opals are less hardy and tend to chip easily. As jewellery adornment, care must be taken to ensure the gem does not receive any heavy impact during use.
|Australia, Mexico, Ethiopia|