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Cachalong opal is a rare, porcelain-white to cream-colored variety of common opal (SiO2·nH2O) characterized by its opaque appearance and waxy luster. This mineraloid, also known as pearl opal or mother-of-pearl opal, forms through low-temperature hydrothermal processes in volcanic rocks.
The mineral exhibits distinctive physical properties, including a Mohs hardness of 5.5-6.0, a specific gravity of 2.1-2.2, and a refractive index between 1.44-1.46. Its microstructure consists of densely packed silica spheres with minimal interstitial water content. Cachalong deposits occur primarily in Kazakhstan, Mongolia, and Indonesia, often associated with chalcedony and other silica minerals.
This material holds cultural significance in Central Asian jewelry traditions, where artisans value its smooth texture and capability to achieve high polish. The name “”cachalong”” derives from the Kalmyk words “”kaltsyun”” (beautiful stone) and “”cholon”” (stone), reflecting its historical importance in the region’s mineralogical heritage.
Cachalong opal is typically a natural gemstone.
Common names for Cachalong Opal include Porcelain Opal, Kašalong, and Milk Opal.
Cacholong opal, like other types 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 scratches and abrasion, so care should be taken when wearing or handling it.
The refractive index of cacholong opal generally falls between 1.440 and 1.460, which is characteristic of opals. This property helps in identifying the gem and evaluating its quality.
Cacholong opal exhibits a waxy to dull luster, distinct from the play of color or iridescence seen in other opals. Its luster contributes to its unique visual appeal, giving it a soft and serene appearance.
Opals, including cacholong opal, typically do not have any cleavage. This means they do not break along any defined plane when subjected to stress.
Cacholong opal commonly displays a conchoidal to uneven fracture, which is typical for opals. This type of fracture can create smooth, curved surfaces on broken pieces.
The specific gravity of cacholong opal ranges around 2.15, which is slightly lower than that of many other gemstones. This property can help in distinguishing it from other materials.
Cacholong opal is isotropic and shows no double refraction under polarized light, which is a key optical property of opals.
Cacholong opal generally lacks the dispersion or “”fire”” that is characteristic of precious opals. It does not show significant play of color.
Opal, including cacholong opal, is amorphous, meaning it lacks a regular crystal structure. This is indicative of its formation process and molecular structure.
Cacholong opal is typically opaque and displays a milky white to light gray color, sometimes with a porcelain-like appearance.
This type of opal is generally opaque, which differentiates it from more translucent or transparent opal varieties.
Cacholong opal does not exhibit pleochroism due to its amorphous structure and opaque nature.
Cacholong opal might exhibit weak fluorescence under UV light, generally showing white or no color, which can help in identifying the gemstone.
Though opals are generally considered to be delicate due to their moisture content and structure, cacholong opal has fair to good toughness, making it somewhat resistant to breakage.
Cacholong opal is brittle, which is a common characteristic of opals, making them sensitive to high pressure or impact.
Being isotropic, cacholong opal does not have an optic sign, which is consistent with its amorphous nature.
Cacholong opal does not typically show a distinctive absorption spectrum, which aligns with its general characteristics as an opal.
Cacholong opal consists primarily of hydrated silicon dioxide (SiO2·nH2O), similar to other opals, but it may contain impurities that give it its opaque and milky appearance.
This effect is generally not present in cacholong opal due to its opacity and lack of fibrous inclusions.
Cacholong opal does not display asterism, as this effect is typically associated with gemstones having a different internal structure.
Unlike some opals, cacholong does not exhibit significant iridescence or color play.
Cacholong opal is not magnetic, which is typical for silicate minerals.
Being a type of opal, cacholong is an insulator and does not conduct electricity effectively.
Cacholong opal is not radioactive, making it safe for handling and wearing as jewelry.
