Danburite
Last updated: April 2026
Danburite is sometimes sold as a colorless diamond substitute or confused with colorless topaz. The sky-blue LW fluorescence is highly distinctive. Key separator from topaz: SG is only 2.97–3.02 vs topaz 3.49–3.57 — danburite will float in methylene iodide (SG 3.32) while topaz sinks.
Physical & Optical Properties
RI Range1.627–1.636
SG Range2.97–3.02
SG Typical3.00
Hardness (Mohs)7–7.5
Crystal SystemOrthorhombic
Optic CharacterDR Biaxial (−)
Birefringence0.006
Dispersion0.017
Fluorescence LWStrong blue
Fluorescence SWStrong blue
Chelsea FilterInert
PleochroismNone
ColorsColorless, Yellow Orange, Red Pink
SpeciesDanburite (CaB₂Si₂O₈)
Key Differentiators
- Strong sky-blue LW and SW fluorescence — highly distinctive
- Much lower SG than topaz (3.00 vs 3.49–3.57) — floats in methylene iodide
- RI 1.627–1.636 — similar range to topaz; use SG to separate
- Biaxial negative
Common Simulants
Treatments
- Irradiation (Russian material — pale yellow)
- Coating (pink color — rare)
Price Context
Natural — low ($/ct)$10
Natural — high ($/ct)$150
NotePer carat; collector gem with limited market demand
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying a danburite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
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