mineral

Howlite

Calcium Borosilicate Hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Chalky white to milky grey with dark brown or black veining; Luster: Sub-vitreous to earthy; Crystal structure: Monoclinic; Cleavage: None; Specific gravity: 2.53-2.59

Hardness: 3
Color: Chalky white to milky grey with dark brown or black veining
Luster: Sub-vitreous to earthy

Identified February 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits, typically in arid environments like playas or lake basins. It is often found as nodules resembling cauliflower heads. It is secondary to borate mineralization in sedimentary environments.

Uses & applications

Used primarily in lapidary work for cabochons, beads, and decorative carvings. It is extremely popular as a low-cost substitute for Turquoise and Lapis Lazuli when dyed.

Geological facts

Howlite was first discovered in 1868 by Henry How in Nova Scotia, Canada. Because of its high porosity, it takes dye very well; blue-dyed howlite is often sold under the trade name 'Turquenite'.

Field identification & locations

Identified in the field by its distinctive spider-web veining and chalky white appearance. It is much softer than natural turquoise (which is 5-6). Major locations include Tick Canyon, California, USA, and various sites in Nova Scotia, Canada.

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