mineral

Howlite (Tumbled)

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Milky white to grey with dark grey or black veins; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Specific Gravity: 2.53-2.59.

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

Identified March 14, 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: Milky white to grey with dark grey or black veins; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Specific Gravity: 2.53-2.59.

Formation & geological history

Howlite is a borate mineral formed in evaporite deposits, usually found in nodules that look like cauliflower heads. It is often found in continental basins associated with volcanic activity or dry lake beds.

Uses & applications

Predominantly used for decorative objects, tumbled stones, and jewelry. Due to its porous nature, it is frequently dyed blue to imitate turquoise or red to imitate coral.

Geological facts

Howlite was first discovered by Henry How in 1868 in Nova Scotia, Canada. It is naturally very soft and can easily be carved into small figurines or beads.

Field identification & locations

Identify in the field by its characteristic 'spider web' veining and white-grey opaque color. It will react slightly to hydrochloric acid. It is commonly found in Nova Scotia (Canada) and California (USA).

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

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

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral