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Ethiopian opal is a hydrated amorphous form of silica (SiO2·nH2O) discovered in 2008 near Wegel Tena, Ethiopia, distinguished by its unique hydrophane properties and remarkable play-of-color characteristics. This precious gemstone forms in volcanic deposits through the precipitation of silica-rich solutions within vesicles and fractures of the host rock.
The stone exhibits exceptional optical phenomena due to its microscopic silica sphere structure, which diffracts light to produce vivid spectral colors. Unlike Australian opals, Ethiopian opals possess a distinctive honeycomb structure that allows them to absorb and release water without damage to their internal structure. The gems range from transparent to opaque, displaying base colors from crystal clear to honey-brown, with some specimens showing rare contra luz opal properties where the play-of-color is visible when light passes through the stone.
Mining occurs primarily in the Wollo province at elevations exceeding 3,000 meters, where the opals formed within layers of volcanic ash approximately 23-33 million years ago during the Oligocene epoch.
Ethiopian Opal is typically a natural gemstone.
Common names for Ethiopian Opal include Welo Opal, Wollo Opal, and Ethiopian Fire Opal.
Ethiopian opal rates between 5.5 and 6.5 on the Mohs scale of hardness. This relatively low hardness means it is more susceptible to being scratched compared to harder gemstones.
The refractive index of Ethiopian opal ranges from 1.42 to 1.43, which is typical for opals and contributes to their unique play of color.
Ethiopian opals exhibit a vitreous to waxy luster, which adds to their visual appeal and the depth of color they display.
Opals, including Ethiopian opals, do not have a cleavage plane. This means they do not break along a defined plane of separation.
These opals usually have a conchoidal or uneven fracture, making them somewhat brittle and sensitive to high pressure or impacts.
The specific gravity of Ethiopian opals typically ranges from 1.98 to 2.20. This measure of density is an indicator of the opal’s ability to display light and color play effectively.
Opals, such as Ethiopian opals, are isotropic gems and do not exhibit double refraction. They have a single refractive index.
Ethiopian opals are known for their impressive play of color, which is a type of dispersion. The internal structure of the opal diffracts light to show various spectral colors.
Ethiopian opals are amorphous, meaning they do not have a crystalline structure. This is typical of all opals.
They can exhibit a wide range of body colors, including white, yellow, orange, red, and a common opal type that is colorless. Their most admired quality is the play of spectral colors across their surface.
Ethiopian opals range from transparent to opaque. The level of transparency affects the value and the type of jewelry for which the opal is suitable.
This gemstone does not exhibit pleochroism due to its amorphous nature.
Some Ethiopian opals may show fluorescence under UV light, typically displaying a greenish hue.
Ethiopian opals are generally fragile due to their high water content and should be handled with care to avoid drying out and cracking.
Opals are generally brittle and have low tenacity, making them susceptible to cracking and chipping.
Being isotropic, Ethiopian opals have an optic sign of “”isotropic.””
Typically, Ethiopian opals do not have a characteristic absorption spectrum, but their color play might affect light absorption in various ways.
Ethiopian opals consist of silica (SiO2) and a variable amount of water. This composition is crucial for the opal’s characteristic play of color.
Some Ethiopian opals can exhibit a cat’s eye effect, though this is less common than in other gemstones like chrysoberyl.
Asterism or the star effect is rare in Ethiopian opals but can occur if the stone has aligned inclusions.
This is one of the defining characteristics of Ethiopian opals, showing a variety of colors that change and move as the stone is turned.
Ethiopian opals are not magnetic.
These opals are non-conductive due to their amorphous silica composition.
Ethiopian opals are not radioactive.
Ethiopian opals are celebrated for their vibrant play of color and are used in various jewelry pieces. However, care must be taken due to their softness and sensitivity to environmental changes.
