GEMSTONE FIELD GUIDE
Topaz
A distinct mineral species; citrine is quartz and should not be called topaz.
Faceted topaz, NMNH G10681. Museum reference photograph; not NumisTrends inventory.
A pear-shaped topaz from the museum's San Luis Potosí collection. Yellow-brown color alone does not distinguish topaz from other materials.
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.
Identify topaz as a mineral, not simply a yellow or blue stone. Citrine is quartz, and the iridescent appearance of marketed mystic topaz comes from a surface coating.
- Refractive index (RI)
- 1.619–1.627
- Specific gravity (SG)
- 3.50–3.57 · typical 3.53
- Mohs hardness
- 8
typical interval
How to read this value
GIA's simplified reference interval, not the entire composition-dependent range. Do not substitute RI measured on one museum topaz for the species range.
How to read this value
Typical value from GIA; general comparison interval from Gem-A's 2022 note on a topaz diamond imitation, not the measured 3.56 of that submitted specimen.
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)1.619–1.627
typical interval
GIA's simplified reference interval, not the entire composition-dependent range. Do not substitute RI measured on one museum topaz for the species range.
Specific gravity (SG)3.50–3.57 · typical 3.53
Typical value from GIA; general comparison interval from Gem-A's 2022 note on a topaz diamond imitation, not the measured 3.56 of that submitted specimen.
Mohs hardness8
Scratch resistance, not toughness. This ordinal scale is not linear.
Birefringence0.008–0.010
GIA encyclopedia's typical range; individual published specimens may differ slightly.
Optic characterBiaxial positive
CleavagePerfect basal cleavage in one direction
A hard blow can split the stone; hardness 8 must not be presented as high toughness.
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?
Citrine quartz
Yellow quartz has historically been sold under misleading topaz names.
How to investigate. A gemologist compares mineral-specific optical properties; citrine and topaz have different published RI profiles.
Trade wording and yellow color do not identify the mineral.
Aquamarine
Blue topaz can offer a similar visual appearance.
How to investigate. Compare the two materials' optical profiles and supporting observations.
Blue intensity does not establish identity or whether color was treated.
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
- Yellow Schneckenstein topaz in the 2022 study appeared inert under the investigators' conventional longwave UV lamps.
- Short-wave UV
- The same study samples also appeared inert under conventional shortwave UV lamps.
These are locality- and study-specific observations, not a rule for all topaz colors. Other excitation methods detected emission; an inert lamp observation does not mean the material cannot luminesce.
Refractive-index profile
Whether optical measurements support topaz rather than a similarly colored mineral.
Reference observation. Published Schneckenstein topaz measurements fell below GIA's simplified headline interval.
Limit. Compare a full gemological profile; do not reject a stone solely because it falls outside one overview interval.
Microscopy of internal breaks and inclusions
Whether observed internal features are consistent with the stone and reveal existing damage.
Reference observation. Gem-A documents iridescence at internal fractures and developing cleavage in topaz.
Limit. This observation alone neither confirms identity nor proves treatment. Never create a cleavage or scratch to test it.
Real laboratory examples
Documented cases, not test results of the reference specimens shown on this page.
Inert under UV lamps, emissive under another excitation
The Schneckenstein study detected chromium-related pinkish-red emission with blue-light excitation despite the samples appearing inert under ordinary UV lamps.
The takeaway. The excitation method is part of the result; do not transfer a laboratory luminescence observation to another lamp or specimen.
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.
Topaz can split along its basal cleavage. Avoid hard blows, strong pressure, abrupt temperature changes, steam and ultrasonic cleaning. Mild soapy water is preferable; abrasives can remove surface coatings.
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 · topaz ↗
- gia.edu · topaz 33572.pdf ↗
- gem-a.com · JoG2022_38_4_corr.pdf ↗
- gem-a.com · ↗
- gia.edu · topaz 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.