mineral

Howlite

Calcium Borosilicate Hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Chalky white with dark grey or black veins; Luster: Sub-vitreous to earthy; Crystal System: Monoclinic; Cleavage: None; Specific Gravity: 2.53–2.59

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

Identified March 9, 2026More mineral →

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Physical properties

Hardness: 3.5 on Mohs scale; Color: Chalky white with dark grey or black veins; Luster: Sub-vitreous to earthy; Crystal System: Monoclinic; Cleavage: None; Specific Gravity: 2.53–2.59

Formation & geological history

Howlite is an evaporite mineral found in sedimentary basins. It typically forms in nodules or cauliflower-like masses within borate deposits. Major deposits are found in maritime provinces of Canada (Nova Scotia) and California, USA.

Uses & applications

Primarily used for decorative carvings, beads, and tumbled stones. Because it is porous, it is frequently dyed blue to imitate Turquoise or red to imitate Coral. It also has minor industrial use as a source of boron.

Geological facts

First discovered in 1868 by Henry How in Windsor, Nova Scotia. It is often referred to as 'White Turquoise' in marketing, though it is chemically unrelated to true turquoise.

Field identification & locations

Identify by its characteristic 'spider-web' grey veining on a porcelain-white background and its relatively soft surface that can be scratched by a copper penny. Tumbled specimens feel smooth but lightweight.

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