COMPARE GUIDE
Blue GlassVSNatural Blue Sapphire
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
- ◎ is higher in Natural Blue Sapphire, giving a numerical distinguishing point.
- ◎ is higher in Natural Blue Sapphire, 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 Glass | B: Natural Blue Sapphire | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.480–1.700 | 1.762–1.770 | B higher |
| Specific gravity (SG) | 2.30–4.50 | 3.95–4.03 | Overlap |
| Mohs hardness | 5.0–6.0 | 9.0 | B higher |
| Birefringence | — | 0.008 | — |
| Dispersion | — | — | — |
| Property | A: Blue Glass | B: Natural Blue Sapphire |
|---|---|---|
| Crystal system | 非晶質 | 六方晶系（三方晶系） |
| Pleochroism | — | 強（青・緑青） |
| Chelsea filter | inert | inert |
| UV (long-wave) | inert | inert |
| UV (short-wave) | inert | inert |
◆Natural blue sapphire (Al₂O₃ corundum, Mohs 9, SG 3.99–4.01, RI 1.762–1.770, doubly refractive, nclusions and characteristic hexagonal color zoning at 10× — glass shows regular round gas bubbles and pressing-die seams. Disclosure as 'glass' or 'imitation blue sapphire' is required under FTC Jewelry Guides §23.25; honest dealers always label the material clearly as 'cobalt-blue glass' or 'Bristol Blue paste' rather than as 'sapphire'.
Distinguishing tools
Tools that decide between Blue Glass and Natural Blue Sapphire 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.