Welo Opal Specialization:
With much of the Opal we specialize for sales at Throwin’ Stones taking origin in Ethiopia, it’s interesting to discuss a bit about it, too!
Wegel Tena (a town in Ethiopia’s north-east) is famed for its Welo opal, which has also been spelled Wello or Wollo. In this mountainous environment, this opal is mined 2500 meters above sea level in the Ignimbrite/Rhyolites layers. Welo opals’ reputation has risen dramatically, and they are now considered superior to opals mined in Shewa (Shewa Province, Ethiopia), which are regarded to be less stable than Welo opals. The dark opals are the debris from the volcanic black ash clouds, and all Ethiopian opal comes from volcanic origin.
Between 1900 and 1928, the well-known Australian fields of Lightning Ridge, Andamooka, and Coober Pedy were all founded. The Ethiopian opal wasn’t discovered until 1990, and commercial manufacturing began in 2008. Ethiopian opal is becoming increasingly popular as an alternative due to its low cost crystal opals, and demand for patterned opals such as honeycomb, snake, and many more that are unique to Ethiopia is increasing.
Earlier in the discussion of Opals, we explored a bit on what causes the “play-of-color” in opal. To understand Opal, we must understand its depth of colors, so let’s recap and expand on this phenomenon.
Some Opals have an unrivaled grandeur and mysticism because of their amazing color play. Opal is one of the most interesting and legendary gemstones because of this.
Many ideas have been proposed to explain the origins of Opal’s color play. The explanation for the color play was found using an electron microscope in the 1960s, when it was revealed that Opal is made up of microscopic silica spheres that may be organized in an ordered manner. The light that enters the stone is diffracted into a spectrum of colors as a result of this. A color sheen or scintillation in the Opal is caused by a light wave diffracted through it. The various hues refracted in the Opal are caused by the density and arrangement of aligned silica spheres. Because the spheres in “common” opal are disorganized or too dense to allow light to refract, it lacks this effect, whereas this effect is seen in “precious” opal.
Certain Opals develop internal and exterior fractures due to a phenomenon known as “crazing.” Crazing is a fascinating phenomena since it is unexpected and lacks consistency. Although it may happen at any time, it generally happens when an Opal is removed from wet circumstances and allowed to dry too rapidly, or when an opal is exposed to bright light, dramatically and hastily (or a combination of these factors). When an opal is subjected to vibration, such as during the cutting and polishing of a specimen, “crazing” can occur. The degree of crazing and the length of time it takes to “craze” differs amongst specimens. The specimen’s origin is frequently a decisive factor in its susceptibility to crazing. In certain circumstances, a very slow drying procedure over months or even years can successfully stabilize the stone and allow it to be cut and polished with less chance of crazing.
Opals that have not been cut are frequently kept in water to prevent crazing. The susceptibility of a specimen rises as it is removed from the water. When storing opal in water, it should not be removed from the water for more than a few minutes at a time. Cutting or polishing Opals, especially those from crazing-prone areas, is a dangerous procedure; whether the Opals craze or not is a question of luck. Opals should not be cleaned with chemicals or detergents, and they should not be exposed to abrupt temperature or lighting changes to avoid crazing.