HOWLITE: California (nodule ~ 3 inches across)
Howlite is always opaque in nodules; it is an abundant material and easy to acquire. Sometimes it contains black, threadlike impurities resembling the veining in turquoise. Howlite is frequently dyed blue to resemble turquoise, and it makes a most convincing simulant. The white material is relatively unexciting in appearance.
Howlite Value
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Howlite Information
| Data | Value |
| Name | Howlite |
| Crystallography | Monoclinic. Crystals tiny; usually nodular masses, chalky or porcellaneous. |
| Colors | White, opaque except in tiny grains. |
| Luster | Subvitreous. |
| Hardness | 3.5 or less. |
| Density | 2.45-2.58. |
| Birefringence | 0.022 |
| Cleavage | Smooth and even fracture. |
| Stone Sizes | Spheres up to about 8 inches in diameter have been cut; also seen as cabochons and tumble-polished stones. |
| Luminescence | Brownish yellow in SW; some California material deep orange in LW. |
| Spectral | Not diagnostic. |
| Formula | Ca2B5SiO9(OH)5 |
| Pleochroism | None |
Optics: a = 1.583-1.586; β= 1.596-1.598; γ= 1.605.
Biaxial (-), 2V large.
Occurrence: Microscopic crystals or nodules occur in arid regions or borate deposits.
California: abundant nodules, up to a weight of several hundred pounds, as at Lang in Los Angeles County Also occurs in the Mohave Desert, California. Nova Scotia: small nodules.
Comments: Howlite is always opaque in nodules; it is an abundant material and easy to acquire. Sometimes it contains black, threadlike impurities resembling the veining in turquoise. Howlite is frequently dyed blue to resemble turquoise, and it makes a most convincing simulant. The white material is relatively unexciting in appearance.
Name: After H. How who described a mineral of approximately the same composition.
