Howlite Value, Price, and Jewelry Information

HOWLITE: California (nodule ~ 3 inches across). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Howlite

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 Information

Data Value
Name Howlite
Colors White.
Crystallography Monoclinic. Crystals tiny; usually nodular masses, chalky or porcellaneous.
Refractive Index 1.583-1.605
Luster Subvitreous.
Hardness 3 - 3.5
Fracture Even and smooth
Specific Gravity 2.45-2.58
Birefringence 0.022
Cleavage None
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.
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long, UV-Short
Enhancements Frequently dyed blue to resemble turquoise.
Typical Treatments Dyeing
Transparency Opaque, except in tiny grains.
Absorption Spectrum 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.

Optic Sign Biaxial -

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.