fasettisina

Fasettisina is a rare and distinctive type of rock crystal known for its unique internal structure and optical properties. The name derives from the Swedish words *fasett* (meaning "facet") and *isina*, referring to its segmented, layered appearance. Unlike traditional quartz, which typically exhibits a uniform internal pattern, fasettisina displays a series of concentric or parallel layers that create a segmented look when viewed under certain lighting conditions.

This phenomenon occurs due to the crystal’s growth patterns, often influenced by environmental factors such as temperature fluctuations or impurities during formation. Fasettisina is commonly found in Sweden, particularly in the regions of Bohuslän and Dalarna, where it is mined from pegmatite veins. The stone is usually transparent to translucent, ranging in color from clear to milky white, though occasional shades of gray or pale yellow may appear.

Optically, fasettisina exhibits a characteristic "cat’s eye" effect or asterism when cut en cabochon, though this is not its defining trait. Its segmented structure can also produce a subtle play of light, giving it an intriguing, almost "faceted" appearance even in raw form. Due to its rarity, fasettisina is highly sought after by mineral collectors and is sometimes used in jewelry, though its unique visual qualities are often appreciated more for their scientific and aesthetic interest than for practical purposes.

The stone’s formation remains a subject of study among geologists, as its layered growth patterns differ from those of more common quartz varieties. Fasettisina is classified as a variety of quartz (SiO₂) and shares many physical properties with other crystalline silicates, including a hardness of 7 on the Mohs scale. While not widely commercially exploited, its distinctive appearance continues to fascinate mineralogists and enthusiasts alike.