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How to Identify Gemstones

At-home tests, what they really prove, and how professionals reach an identification

"What stone is this?" is the question every gem buyer eventually asks — of a ring inherited from a grandmother, a bargain bought on holiday, a parcel from an online seller. Gemmology\'s answer is a ladder: simple checks you can do at home, then instruments, then laboratory confirmation. This guide walks the whole ladder.

The at-home checks (and what they really prove)

Test	How	What it tells you	What it does NOT
Hardness scratch	Scratch tests on known materials (only on inconspicuous spots or scraps!)	Separates very soft imitations (glass, plastic) from harder gems	Identify the stone; and it damages the piece
Heft / density feel	Compare in hand against a known stone of similar size	Obvious fakes (plastic, glass feel light); zircon vs diamond heft differs	Distinguish close relatives
Surface inspection	10x loupe: chips, facet junctions, wear, glue lines, bubbles	Glass (rounded junctions, bubbles) vs crystalline gems; assembled doublets	Name the species
Colour under different light	Daylight vs warm bulb vs torch	Colour-change behaviour (alexandrite, some sapphires); dye that looks flat	Confirm identity
Fog test / thermal feel	Touch to lip or cheek — crystalline stones conduct heat	Plastic and glass feel warm; most gems feel cool	Separate diamond from look-alikes reliably (use a tester)

The honest summary: at-home tests screen — they catch imitations and flag suspects. They never confirm. Anyone promising an identification from a photo or a home test is guessing.

The instrument workflow (how professionals do it)

Professional identification is a process of elimination, not a single magic reading:

General observation — loupe work, colour, transparency, cut, wear, any obvious assembled or dyed features; a gem worksheet structures what to record.
Refractometer — refractive index is a fingerprint-class clue; on faceted stones it eliminates most candidates within seconds, including spot readings for cabochons and optic character for narrowing further.
Specific gravity — hydrostatic weighing or heavy liquids; corundum (~4.0) sinks where quartz (~2.65) floats — density separates look-alikes cleanly.
Polariscope — separates singly vs doubly refractive behaviour instantly, splitting entire mineral families off the list.
Dichroscope — pleochroism check: many coloured stones show different colours along different axes; sapphire does, spinel does not.
UV lamp — fluorescence patterns separate natural from synthetic diamonds, flag filled fractures, expose many dyes.
Microscope — the decisive evidence layer: natural inclusions vs flux or gas bubbles of synthetics, fracture filling, treatment residues.
Spectroscope — absorption lines read like a barcode; a quick check for dyed jadeite or glass-filled ruby.

This exact workflow — with hands-on practice across up to 100 stones — is what JDMIS GT200 Gem Identification Methods teaches in Singapore.

When you need a laboratory

Treatment detection in high-stakes stones (polymer-filled jadeite, heated-vs-unheated sapphire, glass-filled ruby, laboratory-grown diamonds) ultimately needs laboratory instruments and experience. Singapore\'s gem laboratories are profiled honestly in our Singapore gem labs guide. Get the report before paying, not after.

Start identifying right now — free

The JDMIS identification wizard — step-by-step stone ID by colour, clarity and optics
Name That Gem — the game that trains your eye with real instruments
How to identify jade — the A/B/C treatment guide for the stone Singapore asks about most

Common questions

Can I identify a gemstone at home?

You can screen for imitations at home — loupe inspection, heft, colour behaviour and thermal feel catch glass and plastic. Confirming an identification requires instruments (refractometer, specific gravity, microscope) or a laboratory report.

What instruments do gemmologists use?

The standard workflow: loupe observation, refractometer, specific gravity measurement, polariscope, dichroscope, UV lamp, microscope and spectroscope — applied as a process of elimination.

How do I test if a gemstone is real?

"Real" usually means natural and untreated — which home tests cannot establish. Screen at home, then either learn the instrument workflow (a course like JDMIS GT200) or send the stone to one of Singapore's gem laboratories for a report.

Learn this properly — gemmology at JDMIS, Singapore

Everything on this page is taught hands-on at JDMIS with real stones:

Gemmology: Secrets of the Gem & Jewellery Trade (GT100) — teaches the identification habits of the trade — which stones get treated, which tests settle a question, and how dealers actually think
Gem Identification Methods (GT200) — hands-on instrument work: refractometer, specific gravity, microscope and UV, the way professionals actually identify stones.

Free tools while you read: Gem Globe (where stones come from) · Name That Gem (test your eye) · our guide to every Singapore gem laboratory.

Educational content by the gemmology faculty of the Jewellery Design & Management International School (JDMIS), Singapore. Gemmological constants quoted are standard reference values.