COMPARE GUIDE
IoliteVSTanzanite
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
Decisive distinctionsDECISIVE
- ◎ is higher in Tanzanite, giving a numerical distinguishing point.
- ◎ is higher in Tanzanite, giving a numerical distinguishing point.
- ◎ is higher in Iolite, 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: Iolite | B: Tanzanite | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.532–1.553 | 1.690–1.700 | B higher |
| Specific gravity (SG) | 2.55–2.75 | 3.30–3.38 | B higher |
| Mohs hardness | 7.0–7.5 | 6.0–7.0 | Overlap |
| Birefringence | 0.010 | 0.009 | A higher |
| Dispersion | — | — | — |
Optics & fluorescenceOPTICS & UV
| Property | A: Iolite | B: Tanzanite |
|---|---|---|
| Crystal system | 斜方晶系 | 斜方晶系 |
| Pleochroism | 強（青・黄・無色） | 強（青・紫・黄） |
| Chelsea filter | inert | inert |
| UV (long-wave) | inert | inert |
| UV (short-wave) | inert | inert |
ObservationOBSERVATION
◆Tanzanite has much higher RI (~1.69) and SG (~3.35), and stronger trichroism with blue/violet/burgundy axes. The hand-weight difference is obvious.
Color categoriesCATEGORIES
A: Iolite
Purple / Blue
B: Tanzanite
Purple / Blue
DISTINGUISHING TOOLS · 3 ITEMS
Distinguishing tools
Tools that decide between Iolite and Tanzanite 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.