mineral

Howlite

Howlite (Calcium Borosilicate Hydroxide: Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: White to milky white with grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None; Specific gravity: 2.53-2.59

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

Identified May 24, 2026More mineral →

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Physical properties

Hardness: 3.5 on Mohs scale; Color: White to milky white with grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None; Specific gravity: 2.53-2.59

Formation & geological history

Formed in evaporite deposits within sedimentary basins through the precipitation of boron-rich fluids. It is typically found in nodular masses resembling cauliflower.

Uses & applications

Used primarily as decorative carvings, beads for jewelry, and frequently dyed blue or green to imitate turquoise or lapis lazuli.

Geological facts

First discovered near Windsor, Nova Scotia in 1868 by Henry How, a Canadian mineralogist. It is naturally porous, which allows it to take dye very well.

Field identification & locations

Identify by its opaque white color and characteristic 'spider web' veining. It is much softer than the minerals it is often dyed to mimic (like turquoise). Found commonly in California, USA and Nova Scotia, Canada.

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