Howlite
Last updated: April 2026
White to gray calcium borosilicate hydroxide with gray-black veining. Widely dyed blue or turquoise-blue and sold as a turquoise imitation — dyed howlite is the most common turquoise simulant in the commercial market. Strong blue LW UV fluorescence is a key natural identification feature.
Howlite has a specific gravity of 2.53 and a refractive index of 1.583–1.608, with a Mohs hardness of 4. It is aggregate.
Physical & Optical Properties
Key Differentiators
- Natural white/gray color with distinctive gray-black veining resembling spider-web turquoise matrix
- Very low hardness 3.5 — easily scratched by a fingernail or copper coin
- Strong blue LW UV fluorescence (natural undyed material) — diagnostic
- Dyed blue = widely sold as turquoise simulant; acetone definitively removes blue dye
- SG 2.53 lighter than turquoise (2.60–2.85)
Common Simulants
- Turquoise (target of imitation): Dyed howlite is the simulant; turquoise is the target. Turquoise: H 5–6, SG 2.60–2.85, RI 1.610–1.650, no dye on acetone test, no strong blue LW fluorescence.
- Magnesite (also dyed as turquoise): Magnesite (H 3.5–4.5, SG ~3.0) is also dyed blue to imitate turquoise. Higher SG than howlite distinguishes them.
Commonly Confused With
Commonly confused with: Turquoise.
Treatments
- Dyed Blue or Turquoise-Blue (primary treatment)
- Dyed Other Colors (red, green, purple, etc.)
- Wax or Resin Impregnation
Price Context
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Related Comparisons
Measurement Guides
Identifying a howlite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Howlite is one of the 130 species in GemID’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.
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