Tumbled howlite

White to gray, opaque, porcelain-like stone with dark gray veining; Mohs hardness 3–3.5, vitreous to dull luster, triclinic crystal structure, and poor cleavage. The rounded shape indicates tumbling or polishing.

Howlite is a hydrated calcium borosilicate that forms as nodules in evaporite-associated borate deposits, commonly in sedimentary environments. It is geologically young relative to many crystalline rocks, with major deposits known from the Cenozoic western United States.

Used mainly for carvings, beads, cabochons, and ornamental specimens; it is sometimes dyed to imitate turquoise. Its softness makes it unsuitable for heavy-wear jewelry or construction.

Natural howlite is typically white with thin, irregular gray or black veining; turquoise-blue material sold as “turquenite” is often dyed howlite.

Common sources include California and Nova Scotia, Canada. Identify it by its low hardness, chalky white color, irregular web-like veins, and ability to scratch with a steel knife; a photo alone cannot exclude magnesite, marble, or dyed material.