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Liver opal is a rare variety of common opal exhibiting a distinctive reddish-brown to deep mahogany color, closely resembling the appearance of raw liver tissue. The unique coloration stems from high concentrations of iron oxide inclusions within its amorphous silica structure.
This specialized form of opal occurs primarily in volcanic regions, with significant deposits found in Mexico’s Magdalena mining district and Indonesia’s West Java province. The stone lacks the play-of-color characteristic of precious opal, instead displaying a uniform, opaque to translucent appearance with occasional subtle color banding. Its Mohs hardness ranges from 5.5 to 6.0, with a specific gravity of 2.0 to 2.2.
Mineralogists classify liver opal as a hydrated amorphous silica (SiO2¬∑nH2O) containing between 6-10% water content. The stone’s distinctive hepatic hue results from microscopic hematite and goethite particles dispersed throughout its matrix, creating its namesake liver-like appearance.
Liver opal is typically a natural gemstone.
Common names for Liver opal include liver agate, liver stone, and hepatic opal.
Liver opal, similar to other varieties of opal, typically has a hardness of about 5.5 to 6.5 on the Mohs scale. This relatively low hardness means it is somewhat susceptible to scratches and abrasion.
The refractive index of liver opal ranges from 1.44 to 1.46, which is characteristic of opals in general.
Liver opal exhibits a waxy to slightly pearly luster, contributing to its unique visual appeal.
Opals, including liver opal, do not have a defined cleavage. They are generally amorphous without a crystalline structure, which means they break irregularly.
Liver opal typically has a conchoidal fracture, which is a common characteristic among opals, showing smooth, curved surfaces on broken pieces.
The specific gravity of liver opal can range between approximately 1.98 and 2.25, which is fairly typical for opals.
Liver opal is isotropic, meaning it has no double refraction. Opals are amorphous solids without a crystal structure, which results in uniform optical properties in all directions.
Liver opal, like other opals, can exhibit a notable play of color or “”fire””, though the intensity and patterns can vary widely among individual stones.
Being an amorphous mineraloid, liver opal does not have a crystal system.
Liver opal can vary in color but often displays earthy tones such as brown, yellowish-brown, or reddish-brown, which differentiate it from more common opal varieties.
Liver opal ranges from opaque to translucent, depending on the specific conditions under which it formed.
Liver opal does not exhibit pleochroism due to its amorphous nature and isotropic properties.
Opals, including liver opal, can sometimes fluoresce under ultraviolet light, typically showing green or white colors, though this can vary.
Liver opal has fair to good toughness, making it reasonably durable for use in jewelry, though care must be taken due to its relative softness.
Liver opal is generally brittle, which is a characteristic of most opal varieties.
As an isotropic material, liver opal has no optic sign.
Liver opal does not commonly have a specific absorption spectrum due to its amorphous nature.
Liver opal is primarily composed of silica (SiO2) and water, with the water content typically between 3% to 21%.
While not common in liver opal, some specimens might exhibit a cat’s eye effect if the stone has aligned fibrous inclusions.
Asterism is generally not observed in liver opal due to its lack of crystalline structure and necessary inclusions.
The characteristic play of color seen in many opals, including liver opal, is due to the diffraction of light by the microscopic silica spheres within the structure.
Liver opal is not magnetic.
Being composed mainly of silica, liver opal is an insulator and does not conduct electricity.
Liver opal is not radioactive.
