mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

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 →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.

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