How to tell if a demantoid is real
Step-by-step, practical checks you can do at home and with basic tools to decide whether a green demantoid garnet is genuine, and when to send it to a lab for confirmation.
Published
Quick facts
- Type
- the green variety of andradite garnet
- Hardness
- 6.5 to 7 on the Mohs scale
What a real demantoid looks like
Demantoid is the green variety of andradite garnet. Expect a vivid green that can range from yellow-green to slightly bluish-green. Real demantoid often shows lively white sparkle and a strong fire (color flashes) from its high dispersion. Look for bright, clean facets and good brilliance in direct light.
Tell-tale inclusions to inspect
Use a 10x loupe or microscope. A common diagnostic feature for demantoid is a 'horsetail' inclusion: hairlike bundles that resemble fibers radiating from a point. These are not present in most green stones and are a reliable visual clue. Also inspect for crystal inclusions and growth patterns typical of natural garnets; totally inclusion-free glass or synthetic imitations usually lack these internal features.
Quick tests you can do at home
1) Observe dispersion and sparkle: under a bright white light, move the stone and note color flashes. Demantoid shows noticeable fire compared with many green gems. 2) Check with a loupe for horsetail inclusions. 3) Avoid destructive tests: do not attempt to scratch the stone. 4) Compare side-by-side with other green gems you own—differences in brilliance, tone, and inclusions are often obvious.
What professionals check
A gem lab or experienced gemologist will use tools such as a refractometer, spectroscope, and specific gravity measurement, and may examine the stone under higher magnification. They will confirm natural origin and rule out glass fills, dye, or assembled stones. For conclusive identification, request a written report from a recognized gemological lab.
Care, hardness and when to get help
Demantoid has a hardness of 6.5 to 7 on the Mohs scale, so it is softer than ruby or sapphire and can be scratched by harder materials. Clean demantoid with warm soapy water and a soft brush; avoid ultrasonic cleaners if the stone has visible inclusions or treatments. If you need a quick digital check before sending a stone for a lab report, you can also use Jewelry Identifier.
Common questions
- What are horsetail inclusions and why do they matter?
- Horsetail inclusions are thin, radiating fiber-like inclusions often made of chrysotile or similar minerals. They occur in many natural demantoids and are a strong indicator of natural origin because they are difficult to reproduce in glass or simple synthetics.
- Can other green gems be mistaken for demantoid?
- Yes. Stones such as green tourmaline, tsavorite, emerald and green glass can be mistaken for demantoid. Compare brilliance, presence or absence of horsetail inclusions, and overall dispersion. If you cannot distinguish them with a loupe and a light source, seek a professional examination.
- Is a lab report necessary?
- If you plan to buy, sell, insure, or value a demantoid, a lab report provides definitive identification and documents treatments or enhancements. For casual or low-value pieces, careful magnification and the checks listed above may be sufficient.