mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Milky white with dark grey or black veining (spiderweb-like patterns); Luster: Sub-vitreous to dull; Crystal structure: Monoclinic; Cleavage: None visible in massive form.

Hardness: 3
Luster: Sub-vitreous to dull

Identified March 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits through a chemical sedimentary process, specifically in borate-rich saline lakes or basins. Often found in nodules that look like cauliflower heads.

Uses & applications

Primarily used for decorative carvings, sculptures, and jewelry (beads and cabochons). It is well-known for being dyed blue to imitate Turquoise or red to imitate Coral due to its porous nature.

Geological facts

Howlite was first discovered in 1868 near Windsor, Nova Scotia, by Canadian geologist Henry How. In its natural state, it is sometimes referred to as 'white turquoise', though this is a misnomer as they are chemically unrelated.

Field identification & locations

Identify in the field by its characteristic 'cauliflower' nodule shape and gray erratic veining. Because of its low hardness, it can be easily scratched by a copper penny or a knife. Common locations include Nova Scotia (Canada) and Ticino (California, USA).

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