Opal gemstone information and occurrences

Origin:

Opal is an amorphous silicon dioxide found in many regions of the world, with Australia being the best-known source of high-quality opals. Other significant deposits are found in Brazil, Mexico, Ethiopia, and the USA. Opals usually originate in sedimentary or volcanic rocks and form from the deposition of silicon dioxide in fine cracks and cavities.

Special features:

Opals are known for their unique play of colors, also known as "opalescence." Depending on the angle of light, they can reflect different colors, which is due to the microscopic silica spheres contained within the opal. The most common types of opal are white opal, black opal, fire opal (in bright orange and red tones), and boulder opal (opal embedded in a rock). The Mohs hardness of opal is between 5.5 and 6.5, which makes it relatively soft and requires special care.