mineral

Howlite

Hydrous calcium borosilicate (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Milky white to grey with dark grey or black veins; Luster: Sub-vitreous to pearly; Crystal structure: Monoclinic; Cleavage: None (conchoidal fracture); Specific gravity: 2.53–2.59.

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

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits as a result of the evaporation of saline waters in arid environments. It is often found in association with other borate minerals and gypsum.

Uses & applications

Primarily used for decorative purposes, carvings, and in jewelry. Because of its porous nature, it is frequently dyed blue to look like turquoise or red to look like coral.

Geological facts

Howlite was first discovered in 1868 by Henry How in Nova Scotia, Canada. It is nicknamed 'white turquoise' or 'cwhite buffalo stone' though it is chemically unrelated to true turquoise.

Field identification & locations

Identify by its characteristic irregular black or dark grey 'web-like' veins over a white backdrop. It is reactve to hydrochloric acid. Commonly found in California and Nova Scotia.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral