mineral
Howlite
Howlite (hydrated calcium borosilicate; Ca₂B₅SiO₉(OH)₅)
AI-generated identification · may be incorrectWhite to ivory, opaque, with gray-black spiderweb veining; vitreous to subvitreous luster and typically massive rather than visibly crystalline. Mohs hardness 3.5, specific gravity about 2.5–2.6, with indistinct cleavage and uneven fracture.
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Physical properties
White to ivory, opaque, with gray-black spiderweb veining; vitreous to subvitreous luster and typically massive rather than visibly crystalline. Mohs hardness 3.5, specific gravity about 2.5–2.6, with indistinct cleavage and uneven fracture.
Formation & geological history
A borate mineral formed in evaporite deposits, commonly filling cavities or occurring as nodules in arid, alkaline environments; generally associated with Cenozoic sedimentary basins. The pictured piece appears tumbled and polished.
Uses & applications
Used for carvings, beads, cabochons, and ornamental stone; commonly dyed blue and sold as “turquenite” or imitation turquoise. It has little industrial importance.
Geological facts
Howlite is naturally white; strong blue color usually indicates dyeing rather than natural turquoise. Its porous texture accepts dyes readily, making it a frequent substitute for turquoise.
Field identification & locations
Identify it by its soft white body, irregular gray veining, and ability to scratch more easily than quartz; avoid confusing it with magnesite or turquoise. Common localities include California and Nova Scotia, Canada.
