mineral

Howlite

Howlite (Calcium borosilicate hydroxide: Ca2B5SiO9(OH)5)

Hardness: 3.5 on Mohs scale; Color: Milky white to grey with dark grey or black 'spider-web' veining; Luster: Sub-vitreous to earthy; Crystal Structure: Monoclinic; Cleavage: None (conchoidal fracture); Specific Gravity: 2.45–2.58

Hardness: 3
Luster: Sub-vitreous to earthy

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in evaporite deposits within sedimentary basins. It is often found in nodular masses rather than distinct crystals. Primary deposits are found in areas with past volcanic activity where boron-rich fluids interacted with calcium salts.

Uses & applications

Commonly used for decorative carvings, beads, and jewelry. Due to its porous nature, it is frequently dyed blue or green to imitate turquoise (often sold as 'turquenite') or red to imitate coral.

Geological facts

Discovered in 1868 by Henry How in Nova Scotia, Canada. While it looks like marble or turquoise, it is chemically unique as a borosilicate mineral. It is often referred to as 'White Turquoise' in the gemstone market, though this is a misnomer.

Field identification & locations

Identification in the field is noted by its white nodular cauliflower-like appearance and dark erratic veining. It is relatively soft and can be scratched by a copper coin or steel knife. Common locations include Nova Scotia (Canada), California (USA), Turkey, and Germany.

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