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Lithoxyl opal is a rare form of petrified wood where the original organic material has been completely replaced by opal, preserving the cellular structure of the ancient wood in remarkable detail. The mineralization process occurs when silica-rich solutions infiltrate and replace the wood’s organic matter while maintaining its microscopic anatomy.
This gemstone variant exhibits distinctive wood grain patterns and growth rings in opalescent colors, ranging from translucent white to vibrant plays of color. Found primarily in Australia’s Lightning Ridge and White Cliffs regions, lithoxyl opal forms over millions of years through low-temperature diagenesis. The preserved wood structures include tracheid cells, vessels, and medullary rays, making it valuable for both gemological and paleobotanical studies.
The unique optical properties of lithoxyl opal combine the phenomenon of opalescence with fossilized organic patterns, creating specimens that display both precious opal’s play-of-color and the botanical characteristics of the original wood. This dual nature makes it distinct from common opal, precious opal, and other forms of petrified wood.
Lithoxyl opal is typically a natural gemstone.
Common names for Lithoxyl opal include Wood Opal, Petrified Wood Opal, and Fossilized Wood Opal.
Lithoxyl opal has a hardness rating of 5.5 to 6.5 on the Mohs scale, which makes it relatively softer compared to many other gemstones. This means it is more susceptible to scratches and wear.
The refractive index of lithoxyl opal typically ranges from 1.44 to 1.46, which is relatively low compared to other gemstones. This contributes to its unique visual properties.
Lithoxyl opal exhibits a waxy to vitreous luster, contributing to its appealing glow and making it a popular choice in jewelry.
This gemstone does not exhibit any cleavage, which is a common characteristic of opals, making them less prone to splitting along defined planes.
Lithoxyl opal typically has a conchoidal fracture, which is a curved breakage surface resembling the inner surface of a shell. This type of fracture is quite common in more brittle gemstones.
The specific gravity of lithoxyl opal generally ranges from about 2.15 to 2.20, which is considered relatively low, indicating that the stone is less dense than many other gemstones.
This type of opal does not exhibit double refraction due to its amorphous character, which means it lacks a crystalline structure.
Lithoxyl opal can display a range of fire or dispersion, often showing flashes of color when light is refracted inside the stone, although this can vary from stone to stone.
Being an amorphous substance, lithoxyl opal does not have a crystal system. It is made up of silica spheres that are randomly packed together.
The color of lithoxyl opal can vary widely, including white, gray, blue, green, and pink. The presence of additional elements and impurities can influence the coloration.
Lithoxyl opal can range from opaque to translucent, with the degree of transparency affecting its value and use in jewelry.
This gemstone does not exhibit pleochroism due to its amorphous nature, meaning it shows the same color in all directions.
Lithoxyl opal may exhibit fluorescence under ultraviolet light, typically showing a white or greenish glow, which can enhance its appeal.
Opals, including lithoxyl opal, generally have fair to good toughness, but they can be prone to cracking and chipping due to their relative softness and internal structure.
Lithoxyl opal is generally brittle, which is a common trait among opals, making them more susceptible to damage during cutting, setting, or wearing.
As an isotropic gem, lithoxyl opal does not show an optic sign due to its lack of birefringence.
Lithoxyl opal does not typically display a characteristic absorption spectrum, again due to its amorphous nature.
Lithoxyl opal is primarily composed of silica (SiO2) and water, with its water content varying between 3% to 21%.
While not common, some lithoxyl opals can exhibit chatoyancy when cut appropriately, showing a ‘cat’s eye’ effect if fibrous inclusions are present.
Asterism is not typically observed in lithoxyl opal due to the lack of the necessary aligned inclusions that cause this effect.
One of the most striking features of lithoxyl opal is its potential for iridescence, showing a play-of-color caused by the diffraction of light through its silica spheres.
Lithoxyl opal does not exhibit magnetism due to its non-metallic, silica composition.
This gemstone is generally a poor conductor of electricity, consistent with its composition primarily of silica.
Lithoxyl opal is not radioactive and poses no radioactive hazards, making it safe for handling and wear.
