You have a stone at home and want to know what it is. Colour alone will not tell you: the same gem variety comes in many colours, and different gems can look identical to the eye. Professional gemmologists identify stones by testing measurable properties — refractive index, specific gravity, optical character — and eliminating every possibility that does not match. That elimination process is what actually identifies a gem, and while most of it needs laboratory equipment, the first steps can be done carefully at home.
Start with careful observation
Before any tool, gather what your eyes can tell you. Examine the stone in daylight and under a lamp: note the hue, the tone (light to dark), and how evenly the colour is distributed. Look at the cut: is it faceted, cabochon, or carved? Check for chips and wear on the facets — glass imitations scratch and abrade more easily than most crystalline gems. Write everything down; you are building a description to eliminate candidates against a reference list.
Use a 10x loupe
The 10x loupe is the international standard for gem grading, and it is the one professional tool that is genuinely practical to own. Under magnification, look for inclusions — internal features such as crystals, fractures, or growth lines. Inclusions can separate natural gems from their man-made counterparts, and certain inclusions point to specific gem families. A stone that is completely flawless under 10x is itself a signal: either rare, synthetic, or glass.
Run honest home checks
A few non-destructive checks are worth doing. Feel the stone: crystalline gems conduct heat quickly and feel cool to the touch, while plastic and glass feel warmer. If the stone is unset, a simple float test in water tells you whether it floats (amber, some plastics) or sinks (nearly all crystalline gems). What you should not do is scratch, heat, or acid-test a stone — home hardness tests and flame tests can cause irreparable damage, and the internet is rife with such ineffective or bogus methods.
Know where home identification ends
Looks-like elimination and loupe work can narrow the field, but confirming an identity requires measuring properties. A refractometer reading, polariscope behaviour, and specific gravity liquid will conclusively rule candidates in or out — and separating treated from untreated material, or natural from synthetic, generally needs a microscope and spectrometer. At that point the honest options are a gemmological laboratory or learning to use the equipment yourself.
Learning to identify gems properly
Identification is a learnable skill, not a trade secret. At JDMIS the GT100 Gem & Jewellery Trade Secrets course covers gem materials, imitations, synthetics and treatments, and the follow-on GT200 Gem Identification Methods course teaches hands-on lab techniques — loupe work, refractometer, polariscope and spectroscopy — on real stones. For most people, one look through a properly set refractometer explains why the internet’s one-minute tests never quite work.
Where to go deeper
setting a stone once you know what it is · natural vs synthetic diamonds.
Frequently asked questions
Can you identify a gemstone by its colour?
No. The same gem variety comes in many colours and different gems can look identical to the eye. Professionals identify stones by testing measurable properties - refractive index, specific gravity, optical character - and eliminating every possibility that does not match.
What can a 10x loupe tell you about a stone?
Under 10x magnification you can look for inclusions such as crystals, fractures and growth lines, which can separate natural gems from man-made counterparts. A stone completely flawless under 10x is itself a signal: either rare, synthetic, or glass.
Are home hardness and flame tests safe for gemstones?
No. Scratching, heating or acid-testing a stone can cause irreparable damage. Safe non-destructive checks include the heat-conductivity feel test and, for unset stones, a water float test.
Explore further: play Name That Gem, a free gem-identification game, or trace gems to their sources on the Gem Globe.
Visual reference
Try it with a real stone: the JDMIS gem identification tool walks the measurable tests (RI, SG, optic character) with you; the professional toolset behind them is in the eight tools gemmologists use.