mineral
Howlite
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 System: Monoclinic; Cleavage: None; Specific gravity: 2.53-2.59
- Hardness
- 3
- Color
- Milky white to grey with dark grey or black veins
- Luster
- Sub-vitreous to earthy
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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 System: Monoclinic; Cleavage: None; Specific gravity: 2.53-2.59
Formation & geological history
Formed in evaporite deposits, typically in arid environments, as a result of the evaporation of saline waters in basins. Major deposits are found in Canada and the United States (California).
Uses & applications
Primarily used for decorative carvings, jewelry beads, and as an ornamental stone. Because of 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 often called 'White Turquoise' in the gem trade, though this is a misleading marketing name.
Field identification & locations
Identified by its cauliflower-like nodules in the field and its distinctive erratic dark veining. To distinguish from White Magnesite, a hydrochloric acid test or spectroscopic analysis is often needed.
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