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The Fantasy Colors of Opal: Why is it so fascinating?
Opal, a hydrated amorphous silicon dioxide, attracts many gem lovers with its unique optical phenomena and varied colors. Its moisture content is usually between 6% and 10%, but in some rare cases it can reach 21%. The charm of Opal lies not only in its gorgeous appearance, but also in the geological history and formation process hidden behind it.
Opar is considered to be hydrated amorphous silica, and this unique chemical structure explains, in part, why opal cannot be classified as a traditional mineral.
Opal colors range from crystal clear white to mysterious black, with the Black Opal considered the rarest variant. Gemologists divide Opal into precious Opal, which exhibits a game of color, and common Opal, which lacks this optical effect.
The Secret of Precious Opal
The beauty of precious opal lies in the play of colors within it, and this dance of colors comes from the unique arrangement of the microscopic structure within the opal. The structure consists of silica spheres with diameters ranging from 150 to 300 nanometers, which are mostly arranged in hexagonal or cubic close-packed arrangements. In the mid-1960s, scientist J. V. Sanders demonstrated that these ordered silica spheres produce internal color through the interference of light.
The internal structure of opal not only affects its color, but also determines the quality of its gemstone. When the distance between the spheres approaches half the wavelength of visible light, the light will be diffracted, forming colorful light and shadows.
During the formation of precious opal, microcracks may be filled with secondary silica, producing a thin layered structure. This phenomenon is called opal color, also known as color play in gemology. Different opals can show completely different optical effects due to their different transparency.
Common Opal has many variations
Compared with precious Opal, common Opal has more abundant and diverse species. This type of opal may be milky white, or resin opal with an amber-yellow luster. These are not gemstones in the traditional sense, but are still favored by many collectors.
For example, wooden opal is formed by the replacement of the organic matter of wood with opal. Its particularity makes it not only beautiful in appearance, but also reflects the original shape and texture of the wood.
The milky white Opal that is common in daily life shows a hazy luster. This optical effect is called the Opal microscope effect. It is often used as an ornament rather than as a primary gemstone.
Formation and geographical distribution of Opal
The formation of opal mainly depends on geological factors, and different regions produce opal with different characteristics. Australia is considered the world's main producer of Opal, said to produce about 95% of the world's supply of the precious Opal. The Opal produced in Coober Pedy, South Australia, has become synonymous with Opal around the world for its unparalleled color and quality.
Every year, thousands of Opal lovers and miners gather in this small town to explore the treasures of nature. This process is not only a treasure hunt, but also a journey to find inspiration.
In addition, Ethiopia and the United States also produce a considerable amount of Opal, but the yield and quality in these regions vary greatly and are often unpredictable.
Opal's Fraud
As process technology advances, the technology for synthesizing Opal is also evolving. Laboratory-synthesized opal tends to have a regular grain structure, however these artificial gems generally lack the unique optical effects and internal irregularities of natural opal.
While synthetic Opal excels in some aspects, its true charm lies in the traces of natural history and time contained in natural Opal.
Whether natural or synthetic, Opal's unique optical properties and diverse colors make it easy to attract people's attention and become a popular choice for jewelry collection.
Is this beauty and attraction just the brilliance of the material world, or does it have deeper cultural and historical significance that is worth exploring?
