Precious stones have always been highly valued because of their rarity and beauty. We offer you to look at some extraordinary opals found around the world.
An opal called “Opal Butte”, is a crystal unusual in its beauty. It produces an unusual visual effect as if you see the underwater world imprisoned in the stone. And you see it from the bottom up. It seems like you are looking from the bottom of the ocean to the surface, where the sun plays the warm sunrays.
Another curious specimens are petrified wood with opal veins.
Under certain conditions, the fragments of a fallen tree do not perish, they get mineralized, turning into a real stones bizarre. It requires hundreds of years and the lack of air to form the material, resulting in a unique mineral resembling icy shards of wood, covered with glittering splashes of opal or chalcedony.
A fossil egg? No – a geode with opal core
In the areas rich in minerals, one can find geodes – geological formations, having a cavity inside concealing various minerals. In sections? geodes can look extremely bizarre and attractive.
Types of Opals and color
Oxide inclusions of different chemical elements result in to the appearance of color in opals. In the classification of opals in terms of structure more than forty types are distinguished. These include, among others, the following:
Matrix – the noble black opal with small twinkling of other colors.
Arlekine in which colored areas create a mosaic of polygons.
Fire Opal, which opalescent areas are flame-orange.
Normal Opal – opaque stone of diverse coloring.
White (milk), orange-red and dark blue, called black because of the very dark shade opals are used in the jewelry.
The factor by which the stone is evaluated’is the level of opalescence, i.e. the play of color in the specimen.
Properties of opal
Opal is composed of silica particles and water. The water content in the structure ranges from 0.4 to 32%.
Basically,’the properties of opal and the gem’s quality and depend on the water content.
For those stones which are noble, the weight ratio of water to the other elements is in the range of 6-10%. The more water, the more transparent the opal.
When completely dried it becomes completely opaque, it may even crack and crumble.