Opals, a class of their own, are the most colorful gemstones and the world’s most popular phenomenal unique gems, as opals are often called the “Queen of Gemstones”. Many cultures have attributed opals with supernatural origins and powers. Opals share one characteristic: they shine and sparkle in a continually changing display of fantastic colors that is truly exceptional and unsurpassed, which experts describe as “opalescence”, a term created just to describe opal gemstones. For example, Pipe Opals, fossilized squid beak or benemites, are absolutely breaktaking, especially the "The Virgin Rainbow".
Opal gems are made of amorthous silica, SiO2 + nH2O. In other words, opals are simply a combination of non-crystallizated silica and water, thus this is the reason why opal gemstones contain water, usually 6-10%. Microscopic spheres from silica gel inside the opal are what cause interference and refraction of specific wavelengths that is responsible for giving opal gems the unique play of colors, always new and different, and making opals one of the most sought after gemstone in the world at all times.
There are various types of opal gemstones found around the world. The main categories of opals are:
  •       Black opals – these opals are considered the most beautiful and brilliant of all opals. Some black opals are more valued per carat than diamonds like some Harlequin patterns.
  •       Crystal opals - these opals generally has a brown but transparent background and is second in term valuable opals.
  •       White opals – opals in this category are quite inexpensive but many still display excellent play of colors. White opals are share the stage with Black opals in beauty.
  •       Fire opals – these translucent to transparent gems can range from yellow to cherry red. These gemstones are often faceted and may or may not display play of color. Also called Mexican opals.
Other categories include Light and Gray opals.
This gemstone can also be found naturally as a boulder, thin layer of precious opal in dark ironstone or sandstone. Koroit and Yowah nuts are special boulders that contain an excellent play of color within the veins of the stone as a martix that can rival the dazzling and beautiful black opals.
Because quality black opals are quite rare to obtain, doublets and triplets are man made, usually for jewelry. Doublet and triplet opals are created by combining a thin layer of precious opal on dark ironstone, which makes them look like Black opal. Triplets are similar to doublets except triplet opals have an extra transparent layer of glass, plastic, or crystal for additional protection. 
Vast amount of today’s opals, about 95%, come from Southern Australia. Australia, besides making opals its national gemstone, is also the area where black opals are found. In recent years, Ethiopia has produced many high quality opals that rival that from Australia, especially from Welo, where spectacular crystal opals are being found.  
The most famous area is in Australian, called Lightning Ridge, this is the area where the prized and coveted Black opal gemstone is found. Andamooka, also in Australia, an area where mostly Crystal and Light opal gems are found, is made famous because the largest opal ever found came from here, called the "Andamooka Desert Flame". The opal weights 6,843 kilograms.
Precious opals are very valuable and outstanding investment for any serious gem lover, as precious opals appreciates at a rewarding rate. Collectors and investors usually buy two forms of opal: loose stones and fossils.
Opals are best suited for earrings, brooches, and pendants as these generally receive little contact with harder objects, while opal rings require extra care as the opal can be damaged.
This mystic gemstone is symbolic of faithfulness and confidence when given as a gift. Opals are the anniversary gemstone for the 14th and 18th years of marriage. This fiery gem radiates powerful enegry that will surely illuminate any occasion.