COMPARE GUIDE
Blue FluoriteVSBlue Topaz
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
- ◎ is higher in Blue Topaz, giving a numerical distinguishing point.
- ◎ is higher in Blue Topaz, giving a numerical distinguishing point.
- ◎ is higher in Blue Topaz, giving a numerical distinguishing point.
Note: properties whose numeric ranges do not overlap are auto-extracted. Both are measurable with a refractometer or heavy-liquid bath.
| Property | A: Blue Fluorite | B: Blue Topaz | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.433–1.435 | 1.610–1.620 | B higher |
| Specific gravity (SG) | 3.00–3.25 | 3.50–3.57 | B higher |
| Mohs hardness | 4.0 | 8.0 | B higher |
| Birefringence | — | 0.010 | — |
| Dispersion | 0.007 | — | — |
| Property | A: Blue Fluorite | B: Blue Topaz |
|---|---|---|
| Crystal system | 等軸晶系 | 斜方晶系 |
| Pleochroism | — | 中（青・無色） |
| Chelsea filter | — | inert |
| UV (long-wave) | — | inert |
| UV (short-wave) | strong (blue) | inert |
◆Blue topaz (Al₂SiO₄(F,OH)₂, Mohs 8, SG 3.49–3.57, RI 1.609–1.643, doubly refractive orthorhombic, perfect basal in one direction, weak-to-inert ) versus blue fluorite (Mohs 4, SG 3.18, RI 1.434, singly refractive isotropic cubic, perfect octahedral in four directions, strong blue-violet LW-UV ). Topaz is dramatically harder (Mohs 8 versus 4) and shows distinct doubly refractive on the polariscope; fluorite shows the characteristic isotropic dark cross. The refractive-index difference (1.609–1.643 versus 1.434) is unambiguous on the refractometer. The four-direction octahedral of fluorite versus the one-direction basal of topaz is decisive on visual inspection. Most commercial blue topaz is irradiation-treated colourless topaz (the standard market product since the 1970s GIA-validated treatment); blue fluorite colour is generally natural.
Distinguishing tools
Tools that decide between Blue Fluorite and Blue Topaz in practice.
Note: this page is auto-generated from published GIA / CGL reference values. Individual stones, treatments, and synthetics may fall outside these ranges. For a definitive identification, consult an accredited gem laboratory.