mineral
Howlite
Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)
Hardness: 3.5 on Mohs scale; Color: White with grey or black spider-web veining; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Cleavage: None; Specific Gravity: 2.45-2.58
- Hardness
- 3
- Color
- White with grey or black spider-web veining
- Luster
- Sub-vitreous to earthy
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Physical properties
Hardness: 3.5 on Mohs scale; Color: White with grey or black spider-web veining; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Cleavage: None; Specific Gravity: 2.45-2.58
Formation & geological history
Howlite forms in evaporite deposits, usually as nodules or cauliflower-like masses, often found in arid environments associated with borate minerals and gypsum.
Uses & applications
Primary use is in jewelry, beads, and carvings. Because of its porous nature and white color, it is frequently dyed blue to imitate turquoise or red to imitate coral.
Geological facts
Discovered in 1868 near Windsor, Nova Scotia, by Henry How, a Canadian chemist and mineralogist, for whom it is named.
Field identification & locations
Identify by its characteristic grey spider-web veins on a white porcelain-like base. It is much softer than quartz or turquoise. Frequent locations include Nova Scotia, Canada, and various sites in California, USA.
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