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Lechosos opal is a rare variety of white opal characterized by its milky, translucent appearance and distinct play-of-color phenomenon, predominantly found in the Andes Mountains of Peru at elevations exceeding 4,000 meters. The gemstone exhibits a unique combination of opalescence and chatoyancy, displaying vibrant flashes of blue, green, and occasionally red spectral colors against its creamy white base.
The mineralogical composition consists of hydrated silica (SiO2¬∑nH2O) with trace elements of aluminum and iron, forming microscopic spheres of silica that create its distinctive optical effects. Its formation occurs in volcanic host rocks, specifically within rhyolitic tuff deposits, where hydrothermal solutions rich in silica penetrate and fill cavities. The name “”lechosos”” derives from the Spanish word “”lechoso,”” meaning milky, referring to its distinctive appearance. This opal variant typically contains 6-10% water content, contributing to its unique optical properties and requiring specific care to prevent dehydration.
Lechosos Opal is typically a natural gemstone.
Common names for Lechosos Opal include Milk Opal, Opal Lechosos, and Milky Opal.
Lechosos opal, a variety of common opal, typically has a hardness of about 5.5 to 6.5 on the Mohs scale. This makes it relatively softer than many other gemstones and susceptible to scratches and abrasion.
The refractive index of lechosos opal ranges from approximately 1.44 to 1.46, which is relatively low compared to many other gemstones. This contributes to its subtle, soft glow rather than a brilliant sparkle.
Lechosos opal exhibits a waxy to dull luster, distinguishing it from the more flashy play-of-color seen in precious opals. The luster contributes to its milky, soft appearance.
Opal, including lechosos opal, generally does not exhibit cleavage. This means that it does not break along well-defined, flat planes.
Lechosos opal typically has a conchoidal to uneven fracture, which is characteristic of many types of opal. This can make the gemstone somewhat brittle and careful handling is recommended.
The specific gravity of lechosos opal is typically in the range of about 2.15, which is considered relatively light among gemstones.
Lechosos opal is amorphous and does not have a crystalline structure, hence it does not exhibit double refraction.
Unlike its more colorful counterparts, lechosos opal has very low dispersion. This results in minimal fire, which is the play of color typical of precious opals.
Being an amorphous mineraloid, lechosos opal does not have a crystal system. It lacks a long-range, orderly crystal lattice which is typical in crystalline substances.
Lechosos opal is typically white or very light colored, contributing to its name which suggests a milky appearance.
This type of opal ranges from opaque to translucent. The degree of transparency can affect the overall appearance and perceived luster of the stone.
Lechosos opal does not display pleochroism due to its amorphous nature and general lack of color.
Lechosos opal may exhibit weak fluorescence under UV light; however, this can vary depending on the specific specimen and its origins.
Opal is generally considered to have fair to poor toughness due to its brittleness and natural inclusions.
Lechosos opal is brittle, which is common among opals, and can be prone to chipping and cracking if not handled with care.
Being isotropic, lechosos opal does not have an optic sign.
Typically, lechosos opal does not exhibit a notable absorption spectrum due to its lack of color variation and uniformity.
Lechosos opal is primarily made up of silica (SiO2) and a variable amount of water. This composition is similar across different types of opals.
This phenomenon is generally not observed in lechosos opal due to its opaque to translucent nature and lack of fibrous inclusions.
Lechosos opal does not typically display asterism, as this effect is usually associated with gemstones having a more pronounced crystalline structure and reflective inclusions.
Unlike precious opal, lechosos opal generally does not show iridescence or the colorful play of light.
Lechosos opal is not magnetic.
As a non-metallic mineraloid, lechosos opal has very low electrical conductivity.
Lechosos opal is not radioactive.
