mineral

Howlite

Howlite (Ca2B5SiO9(OH)5)

Hardness: 3.5 on the Mohs scale. Color: Milky white to ivory with grey or black spiderweb-like veins. Luster: Sub-vitreous to porcelainous. Crystal System: Monoclinic (rarely found as distinct crystals, usually massive or nodular). Specific Gravity: ~2.58.

Hardness: 3
Color: Milky white to ivory with grey or black spiderweb-like veins
Luster: Sub-vitreous to porcelainous

Identified July 24, 2026More mineral →

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Physical properties

Formation & geological history

Howlite forms in evaporite deposits, typically occurring as nodules in continental marine environments. It is formed through the alteration of calcium- and boron-bearing evaporite minerals in arid alkaline lake environments.

Uses & applications

Widely used for ornamental carvings, beads, cabochons, and decorative items. Due to its porous nature, it is frequently dyed blue or green to imitate turquoise (often sold as 'turquenite'). It is also an source of boron.

Geological facts

Howlite was discovered in 1868 near Windsor, Nova Scotia, by Canadian chemist and mineralogist Henry How, who named it after himself. Natural crystals of howlite are extremely rare, usually less than 1 cm in size.

Field identification & locations

Identified by its distinctive white background with web-like dark veins and relatively soft surface (easily scratched by a pocket knife). Common locations include Nova Scotia in Canada, California and Nevada in the USA, as well as parts of Mexico and Germany.