Danburite — Properties, Tests & Identification

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Danburite has a specific gravity of 3.00 and a refractive index of 1.627–1.636, with a Mohs hardness of 7.0–7.5. It is biaxial −.

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

Diamond: Diamond: extreme hardness (10), thermal probe, RI 2.42, SG 3.52; danburite SG only 3.0.
Topaz: Topaz has perfect basal cleavage and higher SG (3.53); biaxial positive.

Commonly Confused With

Commonly confused with: Diamond, Topaz.

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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Studying for the GIA, FGA, or FEEG practical? Danburite 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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