Rock Identifier
Howlite (Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)) — mineral
mineral

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: White or milky grey with dark grey/black erratic veining; Luster: Sub-vitreous to earthy/dull; Crystal Structure: Monoclinic; Cleavage: None visible in massive form; Specific Gravity: 2.45 to 2.58.

Hardness
3
Color
White or milky grey with dark grey/black erratic veining
Luster
Sub-vitreous to earthy/dull
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Physical properties

Hardness: 3.5 on Mohs scale; Color: White or milky grey with dark grey/black erratic veining; Luster: Sub-vitreous to earthy/dull; Crystal Structure: Monoclinic; Cleavage: None visible in massive form; Specific Gravity: 2.45 to 2.58.

Formation & geological history

Formed in evaporite deposits, typically in continental saline basins. It is often found in cauliflower-like nodules and is geologist-associated with borate minerals. Most deposits are from the Cenozoic era.

Uses & applications

Predominantly used for jewelry, lapidary carvings, and decorative beads. Because it is highly porous, it is frequently dyed blue to imitate Turquoise or red to imitate Coral.

Geological facts

First discovered near Windsor, Nova Scotia in 1868 by Henry How, a Canadian chemist and mineralogist. In its natural white form, it is sometimes marketed as 'White Turquoise' or 'White Buffalo Stone', although it is chemically unrelated to true turquoise.

Field identification & locations

Identify in the field by its characteristic 'spider web' veining and low hardness (it can be scratched by a copper penny or knife). Commonly found in Tick Canyon, California, and Nova Scotia, Canada. Collectors look for large, un-dyed nodules.

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