Howlite is a calcium borosilicate that forms white nodular masses with delicate spider-web black veining. It is widely sold dyed in blue or green to imitate turquoise or chrysocolla — a common substitute in costume jewelry.
Properties
- Formula: Ca2B5SiO9(OH)5
- Crystal system: Monoclinic
- Hardness: 3.5
- Color: White with gray/black veining; commonly dyed blue, green, red
- Streak: White
- Luster: Sub-vitreous to dull
- Cleavage: None (massive)
- Density: 2.5 g/cm³
Occurrence
Type locality: Tick Canyon (California). Major commercial sources: Boron and Death Valley (California), Nova Scotia (Canada). Forms nodules in evaporite/borate deposits.
Identification
White nodular mass + black spider-web veining + softness + association with other borates (ulexite, colemanite, kernite). The “turquoise-howlite” sold in markets is dyed howlite; turquoise is harder (5-6) and a copper aluminum phosphate.
Collector Notes
Dyed “buffalo turquoise” and “white turquoise” jewelry is overwhelmingly howlite. Natural undyed howlite nodules with classic black-on-white veining are themselves attractive cabochon material.
Found at these Localities
- Boron / Death Valley Borate District (波伦/死亡谷硼酸盐矿)
