Howlite
Howlite is a calcium borosilicate hydroxide, Ca2B5SiO9(OH)5, typically found as white to gray nodular masses veined with dark, web-like markings that resemble turquoise. It crystallizes in the monoclinic system but rarely as distinct crystals, forming instead as compact, chalky nodules in borate-rich evaporite deposits. It was first described in 1868 by Canadian geologist Henry How, for whom it is named.
Howlite properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | Ca2B5SiO9(OH)5 |
| Mohs hardness | 3–3.5 |
| Crystal system | Monoclinic |
| Luster | Subvitreous to dull |
| Streak | White |
| Cleavage | None |
| Fracture | Irregular to uneven |
| Specific gravity | 2.45–2.6 |
| Transparency | Opaque |
| Common colors | White with gray veining |
| Rarity | common |
Geology & background
Howlite forms in evaporite deposits rich in boron, precipitating alongside other borate minerals such as colemanite and ulexite in ancient, dried-up saline lake basins. The type locality is Tick Canyon in California's Mojave Desert, and additional deposits occur in Nova Scotia, where How first identified the mineral, as well as in Turkey's borate-rich basins. It typically forms compact, cauliflower-like nodules rather than well-formed crystals, a habit tied to its rapid, low-temperature precipitation from mineral-laden water. Because natural howlite is porous and readily absorbs dye, most howlite sold commercially has been treated to imitate turquoise, lapis lazuli, or other more expensive stones, and buyers should assume any brightly colored 'turquoise-like' howlite is dyed unless proven otherwise. Untreated material is simply chalky white to gray with contrasting gray to black veining.
How to identify Howlite
Howlite typically shows a porcelain-white to gray, chalky surface crossed by irregular gray to black veins, giving it a superficial resemblance to turquoise, especially once dyed. Luster is dull to slightly waxy, streak is white, and hardness is about 3.5, softer than true turquoise. It shows no obvious cleavage and breaks with an uneven fracture. Because dyeing is so common, checking whether color sits evenly in the veining rather than saturating the whole stone is a useful field check.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Howlite is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Howlite worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- Most blue 'turquoise' howlite sold in jewelry is simply dyed, since natural howlite is porous and takes dye extremely well.
- Howlite was named after Henry How, the Canadian geologist and chemist who first described the mineral in Nova Scotia in 1868.
- Its nodules form in ancient evaporated lake basins alongside other borate minerals like colemanite and ulexite.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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