Howlite
Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)
Rock Type: mineral

Physical Properties
Hardness: 3.5 on Mohs scale; Color: White or milky grey with black, grey, or brown veining; Luster: Sub-vitreous, dull, or earthy; Crystal structure: Monoclinic; Specific gravity: 2.45-2.58
Formation & Geological History
Typically formed in evaporite deposits, usually as a result of the alteration of other borate minerals in lacustrine (lake) environments. It was first discovered in Nova Scotia, Canada, in 1868.
Uses & Applications
Used primarily in jewelry making, often dyed to imitate turquoise, lapis lazuli, or red coral. It is also a popular collector's mineral and is used in decorative carvings and ornaments.
Geological Facts
Howlite is naturally white or grey, but because it is quite porous, it is extremely easy to dye. Most 'Blue Turquoise' found in cheap souvenir shops is actually dyed howlite. It was named after Henry How, the chemist who first described it.
Field Identification & Locations
Identify by its characteristic 'spider web' veining and chalky texture. It can be found in Nova Scotia, California, Turkey, and Germany. Collectors often look for specimens that have not been treated or dyed.
Identified on: 5/2/2026
Mode: Standard