mineral

Howlite (tumbled stone)

Howlite, Ca₂B₅SiO₉(OH)₅

AI-generated identification · may be incorrect

White to cream, opaque, with gray branching veining; vitreous to dull luster and commonly massive rather than visibly crystalline. Mohs hardness 3.5–4, uneven to subconchoidal fracture, specific gravity about 2.5–2.6; the rounded form is polished/tumbled.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

A borate mineral forming in evaporite-rich, alkaline environments, commonly in nodules or irregular masses. It is geologically young relative to many silicate rocks, typically associated with Cenozoic lacustrine or evaporitic deposits.

Uses & applications

Used mainly for beads, carvings, cabochons, and inexpensive decorative specimens; it is sometimes dyed to imitate turquoise. Its softness limits construction and industrial use.

Geological facts

The gray spiderweb-like veining is characteristic but can resemble turquoise or magnesite. Howlite is often sold as “white turquoise,” although that trade name is inaccurate.

Field identification & locations

Identify it by its chalky white color, gray webbing, low hardness, and lightweight feel; it can be scratched by a steel knife. Major sources include California and Nova Scotia, Canada, with additional deposits elsewhere.