Emerald vs Peridot: How to Tell Them Apart
Both are green, but peridot has very strong double refraction (doubled back-facet edges are easy to see under a loupe) and is noticeably denser than emerald.
| Property | Emerald | Peridot |
|---|---|---|
| Mineral | Beryl (Be3Al2Si6O18), chromium-coloured | Olivine (magnesium iron silicate) |
| Typical colours | Green to bluish green | Yellow-green to olive green |
| Mohs hardness | 7.5–8 | 6.5–7 |
| Toughness | Poor | Fair |
| Refractive index | 1.577–1.583 | 1.654–1.690 |
| Birefringence | 0.006 | 0.036 |
| Optic character | Uniaxial – | Biaxial + |
| Specific gravity | 2.67–2.80 | 3.28–3.48 |
| Pleochroism | Distinct (bluish green / yellowish green) | Weak |
| Common treatments | Oil or resin clarity enhancement is almost universal | Normally untreated |
| Ultrasonic cleaning | Avoid | Avoid |
How to tell Emerald from Peridot
- DecisiveRefractometer. The refractive index ranges do not overlap (Emerald 1.577–1.583 vs Peridot 1.654–1.690), so a single reading separates them.
- DecisiveSpecific gravity. The SG ranges do not overlap (2.67–2.80 vs 3.28–3.48), so hydrostatic weighing or heavy liquids separate them.
- HelpfulOptic character. Both are doubly refractive, but Emerald is Uniaxial – and Peridot is Biaxial +. A conoscope or an optic-sign test on a refractometer can tell them apart.
- HelpfulBirefringence. Peridot has a birefringence of about 0.036 against 0.006 for Emerald. Look for doubled back-facet edges through the table of the higher one.
- NoteDurability. Emerald (Mohs 7.5–8) is harder than Peridot (Mohs 6.5–7). Do not scratch-test a stone you want to keep.
- NoteTreatments. Emerald: Oil or resin clarity enhancement is almost universal. Peridot: Normally untreated.
Emerald vs Peridot for jewellery
Emerald has a Mohs hardness of 7.5–8 and poor toughness; Peridot has a Mohs hardness of 6.5–7 and fair toughness.
Emerald is almost always clarity enhanced, while peridot is normally untreated. Emerald is usually bluish green; peridot leans yellow-green.
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Educational reference only. Typical published values vary between specimens and sources, and this page is not a gemological laboratory report. Confirm important stones with a recognised gem lab.
Frequently asked questions
What is the main difference between Emerald and Peridot?
Both are green, but peridot has very strong double refraction (doubled back-facet edges are easy to see under a loupe) and is noticeably denser than emerald.
How can I tell Emerald from Peridot?
Refractometer: The refractive index ranges do not overlap (Emerald 1.577–1.583 vs Peridot 1.654–1.690), so a single reading separates them. Specific gravity: The SG ranges do not overlap (2.67–2.80 vs 3.28–3.48), so hydrostatic weighing or heavy liquids separate them.
Which is harder, Emerald or Peridot?
Emerald is harder: it is Mohs 7.5–8, while Peridot is Mohs 6.5–7.
Which is more durable for everyday jewellery, Emerald or Peridot?
Emerald has a Mohs hardness of 7.5–8 and poor toughness; Peridot has a Mohs hardness of 6.5–7 and fair toughness. Toughness describes resistance to chipping and breaking, which matters as much as hardness for rings.
What are the refractive index and specific gravity of Emerald and Peridot?
Emerald: refractive index 1.577–1.583, specific gravity 2.67–2.80. Peridot: refractive index 1.654–1.690, specific gravity 3.28–3.48.
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