mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

AI-generated identification · may be incorrect

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

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

Identified June 25, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed in evaporite deposits as a result of boron-rich mineral reactions in saline environments. Often found in cauliflower-like nodules.

Uses & applications

Primarily used in jewelry as beads or cabochons, often dyed blue to imitate turquoise or red to imitate coral. Used in decorative carvings and as a collector's mineral.

Geological facts

The mineral was named after Henry How, a 19th-century Canadian mineralogist who first described it in Nova Scotia. It is naturally very porous, making it the preferred medium for creating fake turquoise.

Field identification & locations

Identify by its white, chalky appearance and characteristic spider-web like veining (matrix). Found frequently in California and Nova Scotia. In the field, look for opaque white nodules with dark veining.