mineral

Howlite (polished/tumbled)

Howlite — hydrated calcium borosilicate, Ca₂B₅SiO₉(OH)₅

AI-generated identification · may be incorrect

Usually white to cream with distinctive gray-black spiderweb veining; opaque, vitreous to silky luster, monoclinic crystal system, Mohs hardness 3.5, and no prominent cleavage. The rounded shape indicates polishing or tumbling.

Identified September 12, 2026More mineral →

Explore Howlite (polished/tumbled) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms as a borate mineral in evaporite deposits, commonly associated with arid volcanic-basin environments; major material comes from California and Nova Scotia. It is geologically young relative to many crystalline rocks, generally Cenozoic or younger in its principal deposits.

Uses & applications

Used for beads, cabochons, carvings, and inexpensive decorative specimens; it is also commonly dyed blue and sold as imitation turquoise.

Geological facts

Howlite is porous and readily accepts dyes, so intense turquoise-blue color may indicate treated howlite rather than natural turquoise.

Field identification & locations

Identify it by its very low hardness, lightweight feel, white body, and irregular gray veining; it can be scratched by a steel knife, though testing may damage it. Common sources include California, USA, and Nova Scotia, Canada.