mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

AI-generated identification · may be incorrect

Hardness: 3.5 on Mohs scale; Color: Milky white to grey with dark grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None (conchoidal fracture); Opaque.

Hardness: 3
Color: Milky white to grey with dark grey or black veins
Luster: Sub-vitreous to pearly

Identified July 18, 2026More mineral →

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Physical properties

Hardness: 3.5 on Mohs scale; Color: Milky white to grey with dark grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None (conchoidal fracture); Opaque.

Formation & geological history

Formed in evaporite deposits, usually found in nodules that look like cauliflower heads. It is a borate mineral often found in arid climates like the Mojave Desert.

Uses & applications

Primarily used for decorative carvings, jewelry, and beads. It is frequently dyed blue to imitate turquoise or red to imitate coral.

Geological facts

Howlite is naturally very porous, which makes it an ideal candidate for dyeing. It was first discovered in 1868 by Henry How in Nova Scotia, Canada.

Field identification & locations

Identified by its white porcelain-like appearance and spider-web dark veining. To distinguish it from magnesite, a chemical test for boron can be used. It is soft enough to be scratched by a copper coin.