Howlite

Howlite

by Tim Matthews
Published: June 2014
Modified: August 2021
Howlite Polished

Not well known to the general public, howlite is one of those minerals that is almost more famous for imitating another mineral. In this case, the other mineral is turquoise, a phosphate gemstone. Howlite is naturally milky white in color and often has dark vein-like mineral inclusions. Because of its porosity, it accepts dye fairly easily, achieving a turquoise-like blue color. Howlite accepts a nice polish and its porcelain-like luster is appealing.

General Information

Common Name
Howlite
Species
Howlite
Transparency
Semitranslucent - Opaque
Dispersion
Strength: None
Refractive Index
1.586-1.605
Tolerance:(+0.003/-0.003)
Birefringence
0.017- 0.019
Optic Character
Biaxial
Optic Sign
Negative
Polariscope Reaction
Aggregate (AGG), Doubly Refractive (DR)
Fluorescence
SWUV: inert to weak bluish white or brownish yellow; Dyed: brownish yellow
LWUV: Inert to moderate bluish white or orange; Dyed: Inert to orange
CCF Reaction
Dyed blue: pink to red
Pleochroism
None
Hardness
3-3.5
Streak
White
Specific Gravity
2.450-2.590 Typical:2.580
Toughness
Varies
Inclusions
Howlite is often dyed to look like turquoise or lapis lazuli. The stones frequently have a dark gray or black spider web matrix.
Luster
Vitreous, Dull
Stability
Poor
Fracture
Conchoidal to even
Cleavage
None
Chemical Name
Basic calcium silico-borate
Chemical Formula
Ca2B5SiO9(OH)5
Crystal System
Monoclinic
Chemistry Classification
Borate

Howlite Colors

  • Colorless Howlite
    Colorless
  • White Howlite
    White
  • Blue Howlite
    Blue
  • Green Howlite
    Green
  • Brown Howlite
    Brown

Alternate Names

Howlithe, Turquenite, Dyed Howlite

Countries of Origin

Canada; Turkey; United States of America (the); Unknown; China; Mexico; South Africa; Slovakia; Serbia; Germany; Bolivia (Plurinational State of); United Kingdom of Great Britain and Northern Ireland (the)

Care

Normal care for untreated stones. Soluble dilute acids. Avoid harsh chemicals, ultrasonic cleaners, and steaming for stones that have been dyed.