mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: White or milky grey with black, grey, or brown veining; Luster: Sub-vitreous, dull, or earthy; Crystal structure: Monoclinic; Specific gravity: 2.45-2.58

Hardness: 3
Color: White or milky grey with black, grey, or brown veining
Luster: Sub-vitreous, dull, or earthy

Identified May 2, 2026More mineral →

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Physical properties

Hardness: 3.5 on Mohs scale; Color: White or milky grey with black, grey, or brown veining; Luster: Sub-vitreous, dull, or earthy; Crystal structure: Monoclinic; Specific gravity: 2.45-2.58

Formation & geological history

Typically formed in evaporite deposits, usually as a result of the alteration of other borate minerals in lacustrine (lake) environments. It was first discovered in Nova Scotia, Canada, in 1868.

Uses & applications

Used primarily in jewelry making, often dyed to imitate turquoise, lapis lazuli, or red coral. It is also a popular collector's mineral and is used in decorative carvings and ornaments.

Geological facts

Howlite is naturally white or grey, but because it is quite porous, it is extremely easy to dye. Most 'Blue Turquoise' found in cheap souvenir shops is actually dyed howlite. It was named after Henry How, the chemist who first described it.

Field identification & locations

Identify by its characteristic 'spider web' veining and chalky texture. It can be found in Nova Scotia, California, Turkey, and Germany. Collectors often look for specimens that have not been treated or dyed.

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Mineral/Rock

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mineral