mineral

Howlite

Ca2B5SiO9(OH)5

Hardness: 3.5 on the Mohs scale. Color: Milky white to ivory with grey or black spiderweb-like veining. Luster: Vitreous to sub-vitreous, silky or dull when unpolished. Crystal structure: Monoclinic, typically found in nodular or massive form. Cleavage: None visible in massive forms. Specific gravity: ~2.58.

Hardness: 3
Luster: Vitreous to sub-vitreous, silky or dull when unpolished

Identified July 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits, usually within arid sedimentary basins or lakes where boron-rich thermal waters evaporated.

Uses & applications

Widely used for lapidary work, carved decorative objects, beads, tumbled stones, and as an affordable substitute or imitation material for turquoise when dyed.

Geological facts

Howlite is named after Henry How, a Nova Scotian chemist and mineralogist who discovered it in 1868. Because of its porous nature, it easily accepts dye and is frequently dyed blue or green to imitate turquoise, sometimes sold under the trade name 'Turquenite'.

Field identification & locations

Can be identified by its distinctive white chalky base paired with faint to dark dark grey veins, low hardness (easily scratched by a copper penny or glass), and porcelain-like feel when polished. Major sources include Los Angeles and San Bernardino counties in California, as well as Nova Scotia, Canada.