mineral
Howlite (polished/tumbled)
Howlite — hydrated calcium borosilicate, Ca₂B₅SiO₉(OH)₅
AI-generated identification · may be incorrectUsually white to cream with distinctive gray-black spiderweb veining; opaque, vitreous to silky luster, monoclinic crystal system, Mohs hardness 3.5, and no prominent cleavage. The rounded shape indicates polishing or tumbling.
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Physical properties
Usually white to cream with distinctive gray-black spiderweb veining; opaque, vitreous to silky luster, monoclinic crystal system, Mohs hardness 3.5, and no prominent cleavage. The rounded shape indicates polishing or tumbling.
Formation & geological history
Forms as a borate mineral in evaporite deposits, commonly associated with arid volcanic-basin environments; major material comes from California and Nova Scotia. It is geologically young relative to many crystalline rocks, generally Cenozoic or younger in its principal deposits.
Uses & applications
Used for beads, cabochons, carvings, and inexpensive decorative specimens; it is also commonly dyed blue and sold as imitation turquoise.
Geological facts
Howlite is porous and readily accepts dyes, so intense turquoise-blue color may indicate treated howlite rather than natural turquoise.
Field identification & locations
Identify it by its very low hardness, lightweight feel, white body, and irregular gray veining; it can be scratched by a steel knife, though testing may damage it. Common sources include California, USA, and Nova Scotia, Canada.
