Turquoise vs Howlite: How to Spot Dyed Howlite
Last updated: August 2026
Dyed howlite is the most common turquoise imitation in the commercial market. Natural howlite is white to gray with gray-black veining that resembles spider-web turquoise matrix — dye it blue and it passes a glance test convincingly. It does not pass measurement: howlite is far softer (3.5 vs 5–6), noticeably lighter (SG 2.45–2.58 vs 2.60–2.90), reads a lower RI, and its blue comes off with acetone. Turquoise, for its part, carries a diagnostic copper absorption band a hand spectroscope can see.
Property Comparison
| Property | Turquoise | Howlite | Diagnostic? |
|---|---|---|---|
| Hardness | 5 – 6 | 3.5 — easily scratched | Yes |
| SG | 2.60 – 2.90 | 2.45 – 2.58 | Yes |
| RI | 1.610 – 1.650 | 1.583 – 1.608 | Yes |
| Acetone swab | Blue is body color | Acetone removes blue dye | Yes |
| Spectroscope | Cu²⁺ band near 432 nm (strong, diagnostic) | No diagnostic absorption bands | Yes |
| Fluorescence (LW) | Weak blue-white | Strong blue (natural undyed material) | Clue |
| Hot needle | — | Smells acrid when dyed | Clue |
| Luster | Waxy | Waxy | No |
| Structure | Aggregate (opaque), often matrix veining | Aggregate (opaque), gray-black veining | No |
The Definitive Tests
- Hardness check. Howlite is only 3.5 on the Mohs scale — easily scratched by a fingernail or copper coin. Turquoise at 5–6 resists both. Test the back or drill-hole area of a bead, never the display face.
- Acetone swab. On an inconspicuous spot, wipe with a cotton swab dampened with acetone. Acetone definitively removes the blue dye from dyed howlite — blue on the swab ends the question. Genuine turquoise body color does not wipe off (note that dyed turquoise also exists; a blue swab proves dye, not the substrate).
- Specific gravity (loose stones). Turquoise reads 2.60–2.90; howlite reads 2.45–2.58. The ranges do not overlap, and the difference is measurable by hydrostatic weighing even on beads.
- Spectroscope — the copper band. Turquoise is a hydrated phosphate of copper and aluminum, and its Cu²⁺ absorption band near 432 nm is strong, diagnostic, and visible in a hand spectroscope — the most reliable hand-instrument test for copper content. Howlite shows no diagnostic absorption bands.
Common Mistakes
- Trusting the matrix. Howlite's natural gray-black veining resembles spider-web turquoise matrix — the veining is precisely what makes dyed howlite convincing. Matrix appearance proves nothing in either direction.
- Stopping at "not howlite." Dyed magnesite and plastic are also sold as turquoise, and Gilson synthetic turquoise exists. Block/reconstituted turquoise (powder and binder) shows uniform texture, no matrix variation, and mold marks on backs under the loupe.
- Assuming a pass means untreated. Most commercial turquoise is stabilized (resin-impregnated), wax-impregnated, or dyed; untreated natural material is uncommon — mostly fine Persian. The Zachery treatment is not detectable by standard gemological testing at all; EDXRF laboratory analysis is required.
- Over-reading UV. Strong blue LW fluorescence is a key identification feature of natural undyed howlite, but on dyed material the response is less dependable. Use UV as a supporting clue, not the verdict.
Frequently Asked Questions
How can I test whether my turquoise is dyed howlite?
Three accessible checks: (1) hardness — howlite is only 3.5 and is easily scratched, while turquoise is 5–6; (2) an acetone swab on an inconspicuous spot — acetone removes the blue dye from dyed howlite; (3) specific gravity — howlite reads 2.45–2.58 vs turquoise 2.60–2.90. A hot needle also makes dyed howlite smell acrid.
Why does howlite look so much like turquoise?
Natural howlite is white to gray with gray-black veining that closely resembles the spider-web matrix of natural turquoise. Once dyed blue, the veining reads as matrix and the color reads as turquoise — which is why dyed howlite is the most common turquoise imitation on the market. The veining is exactly what makes it convincing, so matrix alone proves nothing.
If it passes these tests, is it natural turquoise?
It is consistent with turquoise, but turquoise itself is commonly treated: most commercial material is stabilized (resin-impregnated), wax-impregnated, or dyed, and untreated natural turquoise is uncommon. Gilson synthetic turquoise also exists, and the Zachery treatment cannot be detected by standard gemological testing — laboratory analysis (EDXRF) is required for that determination.
Checking a turquoise piece? GemID walks you through the scratch, SG, and spectroscope checks and tells you which candidates remain.
Open GemID →Studying for a gemology practical? GemID’s timed exam simulators drill exactly this call — separating look-alike stones by their measured properties.
Practice exams →