Your Purchases
“Pipe opal is a rare form of precious opal found exclusively in Lightning Ridge, New South Wales, Australia, characterized by its distinctive cylindrical or tubular formation within ironstone concretions. The opal forms in vertical pipe-like structures through ancient plant root channels, where silica-rich solutions deposited opal during the Cretaceous period.
These unique specimens exhibit vibrant play-of-color patterns that radiate concentrically from the center of the pipe structure, displaying spectral hues against a dark body tone. The ironstone matrix surrounding pipe opals contains high levels of goethite and hematite, contributing to their stability and preservation. Individual pipe formations range from 1 to 15 centimeters in diameter and can extend several meters in length through the host rock.
Mining pipe opals requires specialized vertical shaft excavation techniques due to their perpendicular orientation within the geological strata. Their rarity, combined with their unusual formation pattern and intense color play, makes pipe opals highly valued among collectors and gemologists.
Amber opal is typically a natural gemstone.
Common names for Pipe opal include Boulder Pipe Opal and Tube Opal.
### Hardness:
Pipe opal, like other forms of opal, has a relatively low hardness on the Mohs scale, typically ranging from 5.5 to 6.5. This makes it somewhat susceptible to scratching and requires careful handling and storage to avoid damage.
### Refractive Index (RI):
The refractive index of pipe opal generally ranges from 1.44 to 1.46, which is similar to other varieties of opal.
### Luster:
Pipe opal exhibits a vitreous to resinous luster, characteristic of opal. When polished, it can display a beautiful, glossy appearance.
### Cleavage:
Opal, including pipe opal, has no cleavage. This means it does not break along defined planes of weakness and contributes to its unique break patterns.
### Fracture:
Pipe opal typically has a conchoidal to uneven fracture, similar to other forms of opal.
### Specific Gravity (SG):
The specific gravity of pipe opal is usually in the range of 1.98 to 2.25, which is typical for opals depending on the amount of water content and inclusion within the stone.
### Optical Birefringence (Double Refraction):
Opal, including pipe opal, is isotropic and does not show double refraction. It has an amorphous structure, meaning it lacks the crystalline structure necessary to split light into two rays.
### Dispersion (Fire):
Opals are well-known for their play-of-color, and pipe opal can exhibit strong dispersion, which refers to the splitting of white light into its spectral colors, creating a “”fire”” effect.
### Crystal System:
As an amorphous mineraloid, pipe opal does not have a crystal system. It lacks a long-range, regular atomic structure.
### Color:
Pipe opal can vary widely in color, displaying hues from white to black, including various shades of green, blue, red, and orange, depending on the conditions under which it was formed.
### Transparency:
The transparency of pipe opal can range from opaque to translucent. The level of transparency can affect the stone’s appearance and value.
### Pleochroism:
Pipe opal does not exhibit pleochroism due to its isotropic nature, meaning it shows the same color in all directions.
### Fluorescence:
Pipe opal may exhibit a weak to moderate fluorescence under UV light, typically showing green or white colors.
### Toughness:
Opal is generally considered to have fair to good toughness, but it can be prone to cracking and chipping due to its internal structure and water content.
### Tenacity:
Opal is brittle in tenacity, which makes pipe opal susceptible to breakage if handled roughly.
### Optic Sign:
Being isotropic, pipe opal does not have an optic sign as it does not double refract light.
### Absorption Spectrum:
Pipe opal generally does not display a distinctive absorption spectrum that is useful for identification purposes.
### Chemical Composition:
Pipe opal is a hydrated form of silica (SiO₂·nH₂O). Its water content can range from 3% to 21%, influencing its physical properties and appearance.
### Chatoyancy (Cat’s Eye Effect):
Some pipe opals can display chatoyancy, a phenomenon seen as a single bright band of light across the surface that moves with the light source, similar to a cat’s eye.
### Asterism (Star Effect):
Asterism or the star effect is rare in opals, including pipe opal, and would typically be more diffuse if present.
### Iridescence:
Pipe opal can exhibit iridescence, especially when it includes layers or inclusions that diffract light to create a rainbow-like effect.
### Magnetism:
Pipe opal is not magnetic and does not respond to magnets under normal conditions.
### Electrical Conductivity:
Opal, including pipe opal, is generally a poor conductor of electricity due to its amorphous and non-metallic nature.
### Radioactivity:
Pipe opal is not radioactive and poses no health risks related to radioactivity.”
