mineral

Howlite

Howlite (calcium borosilicate hydroxide; Ca2B5SiO9(OH)5)

AI-generated identification · may be incorrect

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.

Identified August 25, 2026More mineral →

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Physical properties

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.