mineral
Howlite
Howlite, Ca₂B₅SiO₉(OH)₅
AI-generated identification · may be incorrectWhite to gray, opaque, porcelain-like mineral with dark gray spiderweb veining; Mohs hardness 3.5, vitreous to dull luster, monoclinic crystal structure, and uneven fracture. The pictured piece appears polished or tumbled.
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Physical properties
White to gray, opaque, porcelain-like mineral with dark gray spiderweb veining; Mohs hardness 3.5, vitreous to dull luster, monoclinic crystal structure, and uneven fracture. The pictured piece appears polished or tumbled.
Formation & geological history
Howlite forms as a borate mineral in evaporite deposits, commonly as nodules in arid sedimentary environments. It is geologically young relative to many crystalline rocks, typically associated with Cenozoic borate basins.
Uses & applications
Used primarily for beads, cabochons, carvings, and decorative objects; it is also commonly dyed to imitate turquoise. It has little industrial value.
Geological facts
Howlite is frequently confused with turquoise, but it is softer, usually whiter, and has a more irregular gray web pattern. Some marketed “white turquoise” is actually undyed or dyed howlite.
Field identification & locations
Common localities include California and Nevada, USA, and parts of Canada and Mexico. Identify it by its low hardness, white color, black-gray veining, and ability to be scratched by a steel knife; vinegar does not significantly react.
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Epidote
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Granite
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