GEMSTONE FIELD GUIDE
Emerald
A color variety of beryl, not a separate mineral species.
Trapiche emeralds, NMNH G9127 and G9120. Museum reference specimens; not offered for sale.
Dark radial patterns divide these two trapiche emeralds. The pictured pair is G9127 and G9120; the photo does not establish treatment status.
Photo: Chip Clark / Smithsonian National Museum of Natural History, CC0. · Source ↗ · CC0 1.0 · resized for the webActual source photographs. Each caption identifies its specimen. Alternate photographs are not a 360° scan.
A verified 3D specimen capture is not available for this entry. No generated stand-in is used.
AT A GLANCE
Start with the evidence.
Keep the emerald host, any fracture filler, and any assembled components separate in the interpretation. An inclusion or glow can come from more than one part of the object.
- GIA — Natural, synthetic and treated emerald inclusions (Winter 2016) ↗
- GIA — Quartz assemblage imitating emerald (Summer 2025) ↗
- GIA — Glowing Gems (Winter 2024) ↗
- Refractive index (RI)
- 1.577–1.583
- Specific gravity (SG)
- 2.72 · typical
- Mohs hardness
- 7.5–8
typical interval
How to read this value
GIA's encyclopedia reference is simplified. The same institution's technical review gives broader beryl/emerald principal-index intervals (nω approximately 1.568–1.602; nε approximately 1.564–1.595). Do not reject an emerald solely for falling outside the headline interval.
How to read this value
GIA's variety overview gives a typical 2.72 but no numeric tolerance. The broader 2.6–2.9 in GIA's technical beryl review is not substituted as a variety-specific range.
How to read this value
Scratch resistance, not toughness. This ordinal scale is not linear.
These are reference properties, not measurements of the pictured specimen. Reference images are educational—not NumisTrends sale inventory.
See the details and limitations ↓01 · IDENTIFY
Build a profile, not a guess.
Typical material-level reference; not a measurement, identification, origin, treatment determination, or grading result for any specimen.
Refractive index (RI)1.577–1.583
typical interval
GIA's encyclopedia reference is simplified. The same institution's technical review gives broader beryl/emerald principal-index intervals (nω approximately 1.568–1.602; nε approximately 1.564–1.595). Do not reject an emerald solely for falling outside the headline interval.
Specific gravity (SG)2.72 · typical
GIA's variety overview gives a typical 2.72 but no numeric tolerance. The broader 2.6–2.9 in GIA's technical beryl review is not substituted as a variety-specific range.
Mohs hardness7.5–8
Scratch resistance, not toughness. This ordinal scale is not linear.
Birefringence0.005–0.009
Typical reference range; individual measured birefringence depends on the specimen and measurement orientation.
Optic characterUniaxial negative
CleavagePoor / indistinct basal cleavage
Species-level beryl property. Existing fissures and inclusions can matter more in practical durability.
Open a property for its scope and source. RI and specific gravity have no units. Mohs describes scratch resistance—not resistance to breaking. Do not scratch a stone to test it.
What can look similar?
Tsavorite garnet
Its green color can resemble emerald.
How to investigate. Emerald is doubly refractive; tsavorite is singly refractive. A trained optical examination can distinguish these behaviors.
Do not use color alone.
Synthetic emerald
Its growth and inclusion evidence must be separated from that of natural emerald.
How to investigate. Microscopy can reveal growth-related features; additional laboratory testing may be necessary.
A non-fluorescent response does not rule it out.
Green-cement quartz assemblage
Colorless quartz components can appear green when joined with colored cement.
How to investigate. Examine component boundaries and verify the host material with laboratory methods.
One visually convincing surface does not establish a solid emerald.
02 · TESTS & ULTRAVIOLET
What a test can—and cannot—tell you.
Results depend on the specimen, instrument and method. This is a reference for understanding evidence, not a home authentication or treatment verdict.
UV reaction
- Long-wave UV
- Natural emerald may be red-fluorescent or inert. A Swat Valley study also documented occasional faint yellowish-green responses among usually inert samples.
- Short-wave UV
- Gem-A describes weaker green or inert natural-emerald responses; the regular Swat emeralds in the cited study were typically inert.
Responses vary. Iron-bearing hydrothermal synthetic emerald can be inert too. Filler may glow differently from the emerald host; a fluorescent fracture is not a universal emerald bodycolor response.
Microscopy for inclusions and clarity enhancement
Internal growth evidence and material introduced into surface-reaching fractures.
Reference observation. Flattened bubbles or a flash effect can be evidence of fracture filling.
Limit. Natural, synthetic and treated emeralds require different interpretations; an inclusion chart is not an exhaustive origin test.
Optical identity and assembled-stone check
Whether the green appearance belongs to emerald or to another material or cement.
Limit. GIA's quartz-assemblage case required combined refractive-index, microscopic, spectroscopic and imaging evidence; color alone was misleading.
Real laboratory examples
Documented cases, not test results of the reference specimens shown on this page.
A green appearance created between quartz parts
A GIA case combined three colorless quartz components with green cement. Whitish fluorescence under both longwave and shortwave UV was confined to an internal layer.
The takeaway. Record where a response occurs, not just its color.
Use a qualified gemologist for identification work. Do not expose eyes or skin to UV sources, or perform scratch, heat, acid or solvent tests on a gemstone. Do not assume that an absent UV reaction rules a material out.
03 · TREATMENTS & CARE
Protect the stone you actually have.
Disclosed treatments, fractures and settings can change which cleaning methods are appropriate.
Avoid steam and ultrasonic cleaning of emerald. Heat can extend fractures, and filler can deteriorate; GIA recommends gentle cleaning with warm soapy water.
04 · SOURCES & SCOPE
Know where each fact comes from.
Original NumisTrends explanations with primary references. This is not a replacement for gemological training, a laboratory report, or the examination of your own stone.
Properties reviewed: 2026-09-07 · Identification notes reviewed: 2026-09-07
- gia.edu · emerald ↗
- gia.edu · winter 2019 analytical methods geographic origin determination gemstones ↗
- gem-a.com · JoG1955_5_4.pdf ↗
- gia.edu · emerald care cleaning ↗
NumisTrends is independent of GIA, Gem-A and the museums cited. A matching property cannot by itself establish identity, natural versus laboratory-grown origin, treatment, geographic origin, grade or value.