Emerald
Last updated: April 2026
Emerald is the green to greenish-blue variety of beryl.
Emerald has a specific gravity of 2.72 and a refractive index of 1.565–1.602, with a Mohs hardness of 7.5–8.0. It is uniaxial −.
Physical & Optical Properties
Measured with a polariscope, a refractometer, a hydrostatic balance, a Chelsea filter, a UV torch, a loupe, a darkfield loupe and a spectroscope — step-by-step for each.
Through the refractometer
Drawn from the refractive index above, on a 1.40–1.81 scale. How to take this reading.
Related: Beryl Varieties
Key Differentiators
- Shows red through Chelsea filter
- Characteristic three-phase inclusions
- Low RI and SG
Natural vs. Synthetic
Synthetic emerald is commercially available (Flux (Chatham, Gilson), Hydrothermal (Biron, Linde/Regency, Pool), Lechleitner overgrowth). Distinguishing natural from synthetic typically requires microscopic examination of internal features.
- Microscopy — inclusions: Three-phase inclusions (solid+liquid+gas in one cavity) are definitive for Colombian origin. Also: jagged two-phase inclusions, actinolite needles, biotite, pyrite, irregular fingerprint fractures. Synthetic: Flux (Chatham/Gilson): wispy/cottony flux veils, platinum crystals (metallic reflective platelets), chevron growth patterns (Gilson diagnostic). Hydrothermal (Biron/Linde): nail-head spicules/chrysanthemum inclusions, comma-shaped two-phase inclusions, parallel growth tubes along c-axis. Lechleitner: visible interface between pale natural core and synthetic overgrowth; natural inclusions in core, hydrothermal features in rim.
- UV Fluorescence: Inert to weak red (LWUV). Iron-rich origins (Brazil, Russia) are typically inert. Low-iron Colombian may show weak red. Synthetic: Flux and hydrothermal synthetics: moderate to strong red (LWUV). High Cr content and near-zero Fe produces strong response. Strong red fluorescence is a red flag — but not conclusive alone.
- Chelsea Filter: Weak to moderate pinkish-red. Iron quenches the response. Synthetic: Strong vibrant red or purplish-red. Synthetics are high-Cr / low-Fe, producing a strong filter reaction. Some fine low-iron Colombian naturals can also show strong red — use microscopy to confirm.
- RI: nω 1.565–1.602; SG 2.67–2.78. Synthetic: Flux (Chatham/Gilson): RI nω ~1.560–1.564 (lower than natural — diagnostic). SG ~2.62–2.67. Hydrothermal (Biron/Linde): RI nω ~1.578–1.585 (higher end). SG ~2.67–2.75. A consistently low RI (<1.565) indicates flux synthetic; high RI (>1.580) suggests hydrothermal.
Loupewise Pro includes a two-phase natural vs. synthetic testing protocol for Emerald.
Common Simulants
- Green Tourmaline: Uniaxial negative DR; stronger dichroism; higher RI (1.624–1.644); SG 3.06; no red through Chelsea filter.
- Green Glass: Isotropic; gas bubbles, swirl marks or flow lines under loupe; no dichroism; conchoidal fracture.
- Synthetic green spinel: Isotropic SR; RI ~1.727; Chelsea filter typically red (synthetic spinel fluoresces); no dichroism.
- Tsavorite Garnet: Isotropic SR; no dichroism; RI ~1.740; SG 3.61; Chelsea filter inert (no red).
Commonly Confused With
Commonly confused with: Tourmaline, Glass, Synthetic Spinel, Tsavorite Garnet, Chrome Diopside, Fluorite, YAG.
Treatments
- Cedar Oil / Natural Oil Filling
- Synthetic Resin Filling (Opticon, Permasafe)
- Epoxy Resin Filling (permanent)
Related Comparisons
Measurement Guides
Identifying an emerald? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.
Try Loupewise Free →Studying for the GIA, FGA, or FEEG practical? Emerald is one of the 132 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.
Practice exams →