mineral
Howlite (polished/tumbled)
Howlite, Ca₂B₅SiO₉(OH)₅
AI-generated identification · may be incorrectWhite to pale gray with dark gray spiderweb veining and a waxy to vitreous polish; Mohs hardness 3.5, monoclinic crystal system, poor cleavage, and specific gravity about 2.5–2.6. The specimen appears polished and possibly shaped into a cabochon or palm stone.
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Physical properties
White to pale gray with dark gray spiderweb veining and a waxy to vitreous polish; Mohs hardness 3.5, monoclinic crystal system, poor cleavage, and specific gravity about 2.5–2.6. The specimen appears polished and possibly shaped into a cabochon or palm stone.
Formation & geological history
A borate mineral that forms in evaporite deposits, commonly in arid basins as boron-rich fluids alter sedimentary rocks. It is geologically young relative to many rock-forming minerals; major deposits are associated with Cenozoic evaporite formations.
Uses & applications
Used for beads, cabochons, carvings, and decorative objects; its porous texture is sometimes dyed to imitate turquoise. It has limited industrial use as a borate mineral.
Geological facts
Howlite was named after Canadian chemist Henry How, who described it in 1868. Its characteristic gray veining makes it easy to confuse with turquoise when dyed.
Field identification & locations
Identify it by its white ground, irregular gray veins, low hardness, and light feel; common sources include California, Nova Scotia, and parts of Turkey. Avoid harsh abrasion, since it scratches readily.
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