COMPARE GUIDE
Crystal OpalVSWhite Opal
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
Physical propertiesPROPERTIES
| Property | A: Crystal Opal | B: White Opal | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.430–1.470 | 1.430–1.470 | Nearly equal |
| Specific gravity (SG) | 1.98–2.20 | 1.98–2.20 | Nearly equal |
| Mohs hardness | 5.5–6.5 | 5.5–6.5 | Nearly equal |
| Birefringence | — | — | — |
| Dispersion | — | — | — |
Optics & fluorescenceOPTICS & UV
| Property | A: Crystal Opal | B: White Opal |
|---|---|---|
| Crystal system | 非晶質（含水シリカ） | 非晶質（含水シリカ） |
| Pleochroism | — | — |
| Chelsea filter | — | inert |
| UV (long-wave) | — | weak (white / blue / green) |
| UV (short-wave) | weak (white) | weak (white) |
ObservationOBSERVATION
◆White opal has a milky, opaque-to-translucent body; crystal opal is transparent and lets play-of-color rise from within rather than reflect off a pale background.
Color categoriesCATEGORIES
A: Crystal Opal
Opal
B: White Opal
Opal
DISTINGUISHING TOOLS · 2 ITEMS
Distinguishing tools
Tools that decide between Crystal Opal and White Opal 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.