There are many theories as to how the stone got its name. The Sanskrit word upala, meaning valuable stone is one theory. Some scholars say it came from the Greek word opallios which means color change. Others say that the ancient Romans called it opalus, which means stone of many elements.
There are two different types of the stone. Precious opal which is a stone that has the play of light characteristic, and common opal which does not. Play of light means that reflected and refracted light in many colors can be seen in the stone when viewed from different angles, colors that are different from the main color of the stone. Most gemstones are precious opal but the common type can also on occasion be of gemstone quality. Up until the middle of the 19th century, precious opals were very rare and most were found in what is now Slovenia in Europe. It is now found in Australia and Czech Republic, Hungary, North, South and Central America, and Northern Africa as well as Slovenia.
Not all opals used in jewelry are solid gemstones. Doublets are thin pieces of opal that are fastened to a backing material, while triplets are thin pieces of stone that are attached to a backing material that have a clear quartz cap. There are also synthetic opals being manufactured that are indistinguishable from natural stones except by trained gemologists.
Compared to other gemstones, opal is fragile. Its softness makes it susceptible to damage if not worn with care. It is also a gem that is made up of 3 to 6 percent water. If the stone is exposed to conditions that would dehydrate it, cracks can occur as well as the loss of the play of light. An opal should be worn often to allow the stone to retain its moisture by contact with the air and human skin, and should be mounted in such a way as to give it protection.
There is a great price variation with opals, with the common variety usually much less expensive than the precious. The most expensive precious type of stone is the black opal, which refers to a stone that has a dark main color, and very brilliant flashes. Because precious opal can reflect so many different colors, it can be stylish and match many different types and colors of apparel. As long as care is taken when worn, opal can be worn and enjoyed every day.