mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Chalky white with charcoal-grey or black veins; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Cleavage: None visible in massive form; Specific Gravity: 2.4-2.6.

Hardness: 3
Color: Chalky white with charcoal-grey or black veins
Luster: Sub-vitreous to earthy

Identified April 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits within sedimentary basins, typically where volcanic activity has provided a source of boron. It is often found in massive, cauliflower-like nodules rather than distinct crystals.

Uses & applications

Primarily used as an ornamental stone for carvings, cabochons, and beads. Due to its porous nature, it is frequently dyed blue to imitate turquoise or red to imitate coral.

Geological facts

Howlite was first discovered in 1868 near Windsor, Nova Scotia, by Henry How, a Canadian mineralogist. It is often called 'White Turquoise' or 'Silvery White Buffalo Stone' in the jewelry trade.

Field identification & locations

Identify in the field by its distinct 'matrix' of web-like dark veins against a porcelain-white background. It can be distinguished from magnesite by its chemical reaction to acids and lower hardness.

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