GEMSTONE FIELD GUIDE
Peridot
Peridot is the gem name for Mg-rich olivine near the forsterite end of the forsterite–fayalite series.
Faceted peridot, NMNH G10640. Museum reference photograph; not NumisTrends inventory.
This specimen is cataloged as forsterite, with peridot as a synonym. Its photographed color is not a measurement of chemical composition.
Photo: Ken Larsen / Smithsonian National Museum of Natural History, CC0. · Source ↗ · CC0 1.0 · resized for the webA verified 3D specimen capture is not available for this entry. No generated stand-in is used.
AT A GLANCE
Start with the evidence.
Peridot is gem-quality olivine. Its yellow-green appearance is useful context, but mineral identity needs optical or spectroscopic evidence rather than color alone.
- Refractive index (RI)
- 1.65–1.69
- Specific gravity (SG)
- 3.34 · typical
- Mohs hardness
- 6.5–7
typical rounded interval
How to read this value
GIA's rounded reference interval; composition-dependent values extend beyond a single headline range. Not every stone gives exactly these endpoints.
How to read this value
GIA's overview supplies a typical value without a numeric tolerance; no range invented.
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)1.65–1.69
typical rounded interval
GIA's rounded reference interval; composition-dependent values extend beyond a single headline range. Not every stone gives exactly these endpoints.
Specific gravity (SG)3.34 · typical
GIA's overview supplies a typical value without a numeric tolerance; no range invented.
Mohs hardness6.5–7
Scratch resistance, not toughness. This ordinal scale is not linear.
Birefringence0.035–0.038
Strong double refraction can produce visible doubling of facet junctions in appropriate viewing directions.
Optic characterBiaxial; optic sign may be positive or negative
CleavageTwo imperfect directions
Olivine's imperfect cleavages are described along [010] and [100] in the Gem-A mineralogical discussion; not as perfect easy cleavage.
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?
Green glass
Manufactured green glass can resemble peridot, including unusually brilliant examples.
How to investigate. A published barium-zirconium glass was isotropic; infrared spectroscopy and chemical analysis resolved its identity.
Do not assume glass always has low RI or density, or that inert UV behavior proves peridot.
Demantoid garnet
Green demantoid can be confused with peridot.
How to investigate. Characteristic disc-shaped inclusions can support peridot identification when correctly recognized.
Their absence does not establish garnet: documented brown peridot lacked those familiar inclusions.
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
- All 33 Pyaung-Gaung peridot samples in the Winter 2021 study were inert under longwave UV.
- Short-wave UV
- The same 33 samples were also inert under shortwave UV.
These observations cover the studied material, not every olivine composition. A documented peridot-like glass was also inert at both wavelengths, so absence of fluorescence cannot establish identity. UV examination requires appropriate professional safeguards.
Refractometry and birefringence assessment
Whether measured optical properties fit peridot.
Reference observation. The Pyaung-Gaung study recorded substantial birefringence and a range of RI values across its samples.
Limit. Do not turn a locality's measurements into universal cutoffs; published brown peridot produced higher RI readings than familiar green material.
Microscopy with Raman confirmation
The host mineral and unusual internal crystals.
Reference observation. In a Vietnamese brown-peridot case, Raman confirmed the host and identified threadlike serpentine inclusions.
Limit. Familiar disc-shaped inclusions need not be present. The host and its inclusions require separate interpretation.
Real laboratory examples
Documented cases, not test results of the reference specimens shown on this page.
Brown peridot without the familiar inclusions
Three gems cut from a dark Vietnamese crystal lacked typical disc-shaped inclusions. Their unusual properties prompted Raman confirmation of peridot and its serpentine inclusions.
The takeaway. An atypical inclusion scene is a reason for further testing, not automatic rejection of the material identification.
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.
Clean gently with warm soapy water; avoid ultrasonic and steam cleaners. Protect peridot from hard knocks, scratching and rapid or uneven heating, which can cause fractures.
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 · peridot ↗
- gem-a.com · JoG1998_26_2.pdf ↗
- gem-a.com · JoG2007_30_7 8.pdf ↗
- gia.edu · buyers guide ↗
- gia.edu · peridot 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.