mineral
Howlite egg
Howlite, Ca₂B₅SiO₉(OH)₅; hydrous calcium borosilicate hydroxide
AI-generated identification · may be incorrectCreamy white with dark gray, branching veins; dull to vitreous luster and massive, fine-grained texture. Mohs hardness 3.5; monoclinic mineral, typically without visible crystal faces. The pictured piece is polished and egg-shaped.
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Physical properties
Creamy white with dark gray, branching veins; dull to vitreous luster and massive, fine-grained texture. Mohs hardness 3.5; monoclinic mineral, typically without visible crystal faces. The pictured piece is polished and egg-shaped.
Formation & geological history
Howlite forms as nodules in borate-rich evaporite deposits, often in arid sedimentary basins; it is geologically young relative to many common rocks. The veins are characteristic dark matrix or mineral staining.
Uses & applications
Polished howlite is used for carvings, beads, eggs, and inexpensive decorative objects; it is also dyed to imitate turquoise. It is too soft for most durable jewelry.
Geological facts
Howlite was named for Canadian chemist Henry How, who described it in 1868. Its distinctive dark web-like veining makes it easy to confuse with other white decorative stones.
Field identification & locations
Look for a white-to-cream body with irregular gray veins and low hardness; it scratches more easily than quartz. Notable deposits occur in Nova Scotia, Canada, and California, USA.
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