mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Milky white with fine grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None visible in massive form; Specific gravity: 2.53-2.59.

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

Identified July 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits, howlite was first discovered in 1868 by Henry How in Nova Scotia. It typically forms in nodules that resemble cauliflower heads within gypsum or sedimentary basin environments.

Uses & applications

Commonly used in jewelry for beads and carvings; frequently dyed blue to imitate turquoise or red to imitate coral. Also used in industry as a minor ore of boron.

Geological facts

Howlite is extremely porous, making it the most commonly dyed mineral in the lapidary market. It is often sold as 'White Turquoise' or 'White Buffalo Stone' despite having no relation to turquoise.

Field identification & locations

Identified in the field by its nodular habit and characteristic 'web-like' grey veining. It is much softer than quartz or turquoise and can be scratched by a copper penny or steel knife.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Sandstone with Mineral Veining or Crust

Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)

sedimentary

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

mineral

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock