Howlite
Howlite is a natural calcium borosilicate mineral that forms opaque white nodules, often with grey to black threadlike veining. Because it is porous it is frequently dyed blue as a convincing turquoise imitation. Much of the white material now sold as "howlite" is in fact magnesite, a different mineral (magnesium carbonate).
Products made with this material
No products for this material yet.
Full material guide
What the material is, where it comes from or how it is made, identification and care, from the cited sources.
Properties
| Nature | Natural mineral; often dyed |
| Chemical formula | Ca₂B₅SiO₉(OH)₅ |
| Color | White, often with grey to black veining |
| Crystal system | Monoclinic; crystals tiny, usually chalky or porcelain-like nodular masses |
| Mohs hardness | 3 to 3.5 |
| Specific gravity | 2.45 to 2.58 |
| Refractive index | 1.583 to 1.605 |
| Birefringence | 0.022 |
| Luster | Subvitreous |
| Transparency | Opaque, except in tiny grains |
| Treatment | Frequently dyed, especially blue to imitate turquoise |
Origins & sources
Howlite occurs as microscopic crystals or nodules in arid regions and borate deposits. The International Gem Society notes abundant nodules weighing up to several hundred pounds at Lang, Los Angeles County, and in the Mojave Desert, California, and small nodules in Nova Scotia, Canada. The German gem-testing institute EPI reports that since those deposits dried up, genuine howlite has become rare in the gem trade.
Identification
Howlite is white, soft (3 to 3.5) and opaque, with a refractive index of about 1.58–1.61. Dyed blue howlite imitates turquoise. The EPI institute states that almost all tumbled stones and gemstones offered as howlite are made of magnesite, and that undyed magnesite is also sold as "white turquoise"; neither name describes turquoise. Magnesite can be separated with a carbonate test: its powder fizzes in dilute hydrochloric acid, while howlite does not. Geology.com adds that magnesite has a higher specific gravity (3.0 to 3.2) and a strong birefringence blink on the refractometer. Acid tests are destructive and should only be done on rough or an inconspicuous spot.
Care
Not collected yet
History
Howlite is named after H. How, who described a mineral of approximately the same composition. According to the EPI institute, large quantities of dyed howlite were sold as imitation turquoise especially from the 1960s to the 1990s.
Cultural meanings
Not collected yet
Traditional beliefs
Not collected yet
Collected Oct 23, 2026
- Howlite Value, Price, and Jewelry Information International Gem Society · Accessed Oct 23, 2026 OverviewPropertiesOrigins & sourcesIdentificationHistory
- Magnesite, Howlite & Turquoise Institut für Edelstein Prüfung (EPI) · Accessed Oct 23, 2026 OverviewOrigins & sourcesIdentificationHistory
- Magnesite: A mineral used as a gem and in industry Geology.com · Accessed Oct 23, 2026 Identification
- Magnesite Value, Price, and Jewelry Information International Gem Society · Accessed Oct 23, 2026 OverviewIdentification