mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

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

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

Identified June 24, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Howlite is a borate mineral often found in evaporite deposits, typically forming in nodules that look like cauliflower heads. It is generally found in sedimentary environments such as saline lakes or desert basins.

Uses & applications

Primarily used as a decorative stone in jewelry and carvings. Due to its porous nature, it is frequently dyed blue or green to imitate turquoise (sometimes called 'Turquenite') or red to imitate coral.

Geological facts

It was first discovered in 1868 by Henry How in Nova Scotia, Canada. While it looks like marble, its chemical composition as a borosilicate mineral is much more complex.

Field identification & locations

Identify in the field by its characteristic 'spider-web' or 'matrix' veining and chalky white color. It can be distinguished from magnesite by its lower density and boron content. Common locations include Canada (Nova Scotia) and the USA (California).

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