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Lemon opal is a rare variety of precious opal displaying a distinctive yellow to golden-yellow body tone, characterized by its play-of-color phenomenon within the visible spectrum of 400-700 nanometers. This silica-based mineraloid contains 6-10% water content and forms through the deposition of silica gel in rock cavities.
The gemstone exhibits potch and precious opal zones, with the precious sections displaying vibrant spectral colors through diffraction of light by uniformly-sized and regularly-packed silica spheres. These spheres, ranging from 150 to 400 nanometers in diameter, create the stone’s unique optical properties. Lemon opal’s yellow coloration stems from trace elements of iron oxide within its chemical structure.
Found predominantly in Ethiopian deposits, particularly the Wegel Tena region, lemon opal forms in volcanic host rocks under specific geological conditions requiring alternating wet and dry periods. The stone ranks 5.5-6.5 on the Mohs hardness scale and possesses a refractive index of 1.37-1.47, with specific gravity ranging from 1.98-2.20.
Lemon OpalCommon names for Lemon Opal include Citrus Opal, Yellow Opal, and Canary Opal. is typically a natural gemstone.
Lemon Opal
Lemon Opal has a hardness of about 5.5 to 6.5 on the Mohs scale, making it relatively softer compared to many other gemstones. This level of hardness indicates that while it has decent resistance to scratches, it still requires care during handling and setting in jewelry.
The refractive index of Lemon Opal typically ranges from 1.44 to 1.46. This property helps in identifying the gemstone and also influences the light play visible within the stone.
Lemon Opal exhibits a waxy to dull luster, which is characteristic of opals. This type of luster gives the stone a soft glow that enhances its visual appeal.
Lemon Opal does not have any natural planes of cleavage. This absence makes it less likely to split along defined lines when being cut or if subjected to impact.
The fracture in Lemon Opal is typically conchoidal (shell-like), which is a common characteristic in amorphous minerals. The smooth curvature of the fracture surfaces contributes to the gem’s polished appearance.
The specific gravity of Lemon Opal ranges from approximately 2.1 to 2.3. This relatively low density makes it lighter than many other gemstones, which can be advantageous for larger jewelry pieces.
Lemon Opal does not exhibit double refraction due to its amorphous nature. This means that light rays passing through the gem are not split into two separate paths.
The dispersion or “”fire”” of Lemon Opal is generally low. Unlike its more famous relatives like the precious opal, it does not typically display a significant play of color or fire.
Lemon Opal is amorphous, meaning it does not have a crystalline structure. This lack of internal order contributes to its unique visual properties and softer physical characteristics.
The color of Lemon Opal ranges from pale yellow to a rich, bright lemon-yellow, sometimes with a hint of green. The intensity and uniformity of the color can vary, influencing the value and appeal of the stone.
Lemon Opal can range from translucent to opaque. The level of transparency affects the visual depth and color saturation of the stone, with more translucent specimens typically being more valued.
Lemon Opal does not exhibit pleochroism due to its amorphous nature. This means the color remains constant regardless of the angle from which it is viewed.
Lemon Opal may show weak to moderate fluorescence under UV light, typically emitting a greenish or white glow, although this can vary depending on the specific properties of the stone.
The toughness of Lemon Opal is generally fair to good. Although it is not particularly brittle, care should still be taken to avoid sharp blows or extreme pressure.
The tenacity of Lemon Opal is generally considered brittle. It can be prone to chipping or cracking if subjected to harsh impacts or stress.
Being amorphous, Lemon Opal does not have an optic sign associated with crystalline minerals.
Typically, Lemon Opal does not show a distinctive absorption spectrum due to its amorphous nature and lack of significant color-causing elements.
Lemon Opal is primarily composed of hydrated silicon dioxide (SiO2·nH2O). The water content can vary, which slightly influences the physical properties of each specimen.
This optical effect is rare in Lemon Opal. The cat’s eye effect requires aligned fibrous inclusions or structures, which are generally absent in opal.
Lemon Opal does not typically exhibit asterism. The star effect is associated with the presence of aligned inclusions, which are not characteristic of this type of opal.
Lemon Opal generally does not display iridescence, which is a play of color seen in some other types of opal like precious opal.
Lemon Opal is not magnetic. This property can help differentiate it from some synthetic or imitation gemstones that might show magnetic properties.
Lemon Opal is an insulator, showing very low to negligible electrical conductivity. This characteristic is consistent with its composition as a non-metallic mineral.
Lemon Opal is not radioactive. This makes it safe for all types of jewelry and handling without any health risks.
