Opal is a gorgeous semi-precious gemstone that has been alluring people for centuries with its distinct beauty. It is famed for showcasing a vivid play-of-color that has often been compared to the galaxy, a rainbow and fireworks. The term ‘play-of-color’ can be described as an optical phenomenon that causes the gem to flash various hues and patterns when it is moved or due to a reaction with light. This characteristic makes each opal different from the other.

This stunning gem is closely related to the quartz mineral, and its chemical composition includes millions of tiny, amorphous silica spheres. These spheres cause the stone to diffract light and take on numerous colors from different angles. In addition to the size of the silica spheres, the proportion of other minerals mixed within the stone is responsible for the opal’s color. Hence, you can find this stone in a variety of hues, such as black, brown, pink, red, blue, white and more.

While green, white and blue-toned opals are commonly available, the ones that display black and red hues are extremely rare. Most opals are fairly opaque, but it’s possible to find some that are more transparent than the others. Some of the most popular types of naturally occurring opals are boulder opal, black opal, white opal, matrix opal, crystal opal and fire opal.

As with all gems, synthetic and imitation opals can be found in the market, however readily available and naturally occurring opals get more preference. Approximately 97% of the world's opal supply comes from Australia, and it’s also the national stone of the country. This gem is also mined in Mexico and several other countries across the globe.