mineral

Howlite

Howlite (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: White to milky white with dark grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None; Specific Gravity: 2.45 - 2.58.

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

Identified April 7, 2026More mineral →

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Physical properties

Hardness: 3.5 on Mohs scale; Color: White to milky white with dark grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None; Specific Gravity: 2.45 - 2.58.

Formation & geological history

Formed in evaporite deposits in arid environments. It is a calcium borosilicate hydroxide mineral commonly found in sedimentary basins as nodules.

Uses & applications

Used primarily in lapidary work for carvings and jewelry beads. Due to its porous nature, it is frequently dyed to imitate turquoise, lapis lazuli, or coral.

Geological facts

Howlite was first discovered in 1868 near Windsor, Nova Scotia, by Canadian mineralogist Henry How. It can produce a faint orange fluorescence under UV light.

Field identification & locations

Identify in the field by its characteristic 'spider-web' dark veining and soft, chalky appearance. It is much softer than the minerals it often imitates (like turquoise), making a scratch test a common identification method.