mineral
Howlite
Howlite (calcium borosilicate hydroxide; Ca2B5SiO9(OH)5)
AI-generated identification · may be incorrectWhite to gray, opaque, with dark gray spiderweb veining; vitreous to silky luster and usually massive rather than visibly crystalline. Mohs hardness 3.5, uneven to subconchoidal fracture, no prominent cleavage, and specific gravity about 2.5–2.6; this specimen is polished and tumbled.
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Physical properties
White to gray, opaque, with dark gray spiderweb veining; vitreous to silky luster and usually massive rather than visibly crystalline. Mohs hardness 3.5, uneven to subconchoidal fracture, no prominent cleavage, and specific gravity about 2.5–2.6; this specimen is polished and tumbled.
Formation & geological history
A borate mineral formed in evaporite deposits and boron-rich clay environments through low-temperature hydrothermal or sedimentary processes, commonly in Cenozoic deposits. Major sources include California and Nevada, USA, and parts of Canada and Turkey.
Uses & applications
Used for beads, cabochons, carvings, and ornamental polished stones; it is also commonly dyed blue and sold as imitation turquoise. Its softness limits architectural and industrial use.
Geological facts
Howlite is named after Canadian chemist and geologist Henry How. Its porous structure accepts dyes readily, making undyed white howlite useful for recognizing dyed imitation turquoise.
Field identification & locations
Identify it by its chalky white body, irregular gray-black veining, low hardness, and light weight; it can be scratched by a steel nail. Common localities include Tick Canyon, California, and Nova Scotia, Canada.
