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Red SpinelVSNatural Ruby
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
Decisive distinctionsDECISIVE
- ◎ is higher in Natural Ruby, giving a numerical distinguishing point.
- ◎ is higher in Natural Ruby, giving a numerical distinguishing point.
- ◎ is higher in Natural Ruby, 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.
Physical propertiesPROPERTIES
| Property | A: Red Spinel | B: Natural Ruby | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.712–1.736 | 1.762–1.770 | B higher |
| Specific gravity (SG) | 3.58–3.61 | 3.97–4.05 | B higher |
| Mohs hardness | 8.0 | 9.0 | B higher |
| Birefringence | — | 0.008 | — |
| Dispersion | — | — | — |
Optics & fluorescenceOPTICS & UV
| Property | A: Red Spinel | B: Natural Ruby |
|---|---|---|
| Crystal system | 等軸晶系 | 六方晶系（三方晶系） |
| Pleochroism | — | 強（紫赤・黄赤） |
| Chelsea filter | red | red |
| UV (long-wave) | medium (red) | strong (red) |
| UV (short-wave) | weak (red) | weak (red) |
ObservationOBSERVATION
◆Ruby is doubly refractive with subtle and clear dichroism. Spinel is singly refractive with neither.
Color categoriesCATEGORIES
A: Red Spinel
Red / pink
B: Natural Ruby
Red / pink
DISTINGUISHING TOOLS · 3 ITEMS
Distinguishing tools
Tools that decide between Red Spinel and Natural Ruby 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.