Opals are no doubt one of the most spectacular gemstones that the nature has ever created. This stone is very unique due to its very special composition. In contrast to many other stones, the opal is a mineraloid, not a mineral, this so due to the lack of a definite chemical composition. It has millions of tiny silica spheres in its composition that in its turn creates a unique quality of opals called “play of color”. Only opals have this ability and no other gemstone is able to duplicate opal’s color combination.
The color of this gemstone depends on the size of spheres. Those that are 0.1 micron in their diameter create a violet color, those that are about 0.2 micron in their size create red hue. Everything that is in the middle produces intermediate shades. Since each gemstone has always unique and different size there can’t be exactly two the same color composition, there will always be some degree of differentiation.
There are four main types of opals. Among them are two the most wide spread kinds: white, with white or light gray body color and fire opals that usually have yellow, brown, red or orange body color. Supply of those two types are generally available in various sizes and can be accessed in most places. The third type is a boulder opal’s one that has generally a dark body tone. This type of opal has a solid brown ironstone matrix, its color is mixed with ironstone to some level. The fourth type, black opal one, has a black or some other dark body color and its supply is extremely limited worldwide.
Opals are very soft and delicate gemstones. They are generally rated as a 5.5 to 6.5 on the hardness scale. They should not be exposed to sudden temperature changes or high heat because heat may cause fracturing of the stone. Light is usually well tolerated unless heat from intense light is substantial which in turn may cause some level of fracturing. These stones should never get too dry, this situation may also lead to cracking. To keep opals from drying, one may decide to immerse them in water for a couple of hours from time to time.
It also should be noted that there is some evidence that opals are formed from rain. When the water from rain evaporates the silica that is left behind dries out and after some time hardens forming a precious gemstone. There is also confirmation that that opal is found on Mars. Interestingly, it is the only gemstone but for peridot that is found outside of our planet.
Nowadays, Australia is the biggest producer of opals. In fact, the most valuable opals come from New South Wales and Queensland regions of this country. Those two states are the main producers of this gemstone since 1870’s. Among other places where opals are found are the USA, South America, Mexico, Canada, Britain, Slovakia and Czech Republic.
The stone is usually used as a present for the 14th year of marriage and also a birthstone of the month of October. Arabic legends viewed this gemstone as the one that falls from the heaven, the ancient Greeks regarded opals as the stone that guards people from diseases and Europeans viewed them as a gemstone’s manifestation of purity, truth and hope. In Medieval times, the stone was believed to have an ability to preserve the blond hair from darkening. In Asia, the stone is largely considered to be a symbol of hope.