mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Milky white to grey with dark grey or black veins; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Cleavage: None (conchoidal fracture); Specific Gravity: 2.53-2.59

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

Identified May 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits in arid environments, typically as nodules in sedimentary basins. Primarily found in borate-rich lacustrine environments.

Uses & applications

Commonly used in jewelry as cabochons and beads; often dyed to imitate turquoise, lapis lazuli, or coral. Also used for ornamental carvings and as a magnesium source.

Geological facts

Howlite is porous, making it one of the most frequently dyed minerals in the gemstone industry. It was first discovered in 1868 near Windsor, Nova Scotia, by Canadian geologist Henry How.

Field identification & locations

Identify in the field by its distinct 'spider web' veining (matrix) and low hardness (scratched by a copper coin). Primarily found in Tick Canyon, California, and Nova Scotia, Canada.

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