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Black SpinelVSBlack Zircon
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
- ◎ is higher in Black Zircon, giving a numerical distinguishing point.
- ◎ is higher in Black Zircon, giving a numerical distinguishing point.
- ◎ is higher in Black Spinel, 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: Black Spinel | B: Black Zircon | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.712–1.736 | 1.810–1.984 | B higher |
| Specific gravity (SG) | 3.58–3.90 | 4.00–4.70 | B higher |
| Mohs hardness | 8.0 | 6.0–7.5 | A higher |
| Birefringence | — | 0.020 | — |
| Dispersion | — | 0.039 | — |
| Property | A: Black Spinel | B: Black Zircon |
|---|---|---|
| Crystal system | 等軸晶系 | 正方晶系 |
| Pleochroism | — | — |
| Chelsea filter | — | — |
| UV (long-wave) | — | — |
| UV (short-wave) | inert | inert |
◆Black zircon (ZrSiO₄, Mohs 6.5–7.5, SG 4.6–4.7, RI 1.810–2.024 — among the highest of all gem minerals, strongly doubly refractive uniaxial positive tetragonal with dramatic 0.039, characteristic of back edges visible at 10×, opaque to translucent deep black) versus black spinel (Mohs 8, SG 3.58–3.90, RI 1.712–1.736, singly refractive, no ). The test is unambiguous: black zircon shows dramatic of back edges visible without magnification on larger stones while black spinel shows no oubling' is a classical diagnostic test in gemology coursework.
Distinguishing tools
Tools that decide between Black Spinel and Black Zircon 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.