Is every red corundum a ruby?

Ruby is the red variety of corundum, with chromium producing the red colour. The commercial boundary between pink sapphire and ruby can involve accepted gem-trade judgement, so colour naming is not a simple home test.

Is ruby harder than garnet?

Yes. Ruby is corundum at Mohs 9, while common garnets are generally about 6.5 to 7.5. Do not use a destructive scratch test on jewellery or a potentially valuable specimen.

Can garnet look exactly like ruby?

Some red garnets can closely resemble ruby in ordinary viewing. Crystal form, optic character, refractive index, spectrum, inclusions, and other gemological measurements provide stronger evidence than colour alone.

Does UV fluorescence prove a stone is ruby?

No. Many rubies fluoresce because of chromium, but intensity varies with chemistry and treatment, and fluorescence is not unique enough to authenticate a stone by itself.

How can I tell whether a ruby is natural or laboratory-grown?

That distinction generally requires trained microscopy and gemological or advanced laboratory testing. A qualified report can identify the material and state whether laboratory growth or detectable treatments are present.

Built by a geologist

Ruby vs Garnet: Hardness, Crystal Form and Optical Clues

Red colour alone cannot separate ruby from garnet. Ruby is red corundum, typically Mohs 9 with trigonal crystals that may look barrel-shaped or hexagonal in outline. Garnet is a compositionally variable mineral group, commonly Mohs 6.5 to 7.5 with isometric dodecahedral or trapezohedral forms. Transparent material, cut stones, synthetics, treatments, inclusions, and mixed deposits can defeat simple field tests. Non-destructive optical and gemological measurements are safer and more defensible than scratching a valuable stone. On rough expendable material, crystal form and a carefully controlled hardness comparison can separate typical specimens: ruby is corundum at Mohs 9, while garnet is generally 6.5 to 7.5. Ruby may show direction-dependent colour or optical behaviour, whereas garnet is singly refractive and typically shows the same colour in all directions. Valuable, cut, mounted, synthetic, or treated material requires a gemological laboratory report. Record whether the material is rough, cut, mounted, inherited, treated, or sold with a report. Preserve receipts, disclosures, provenance, and any original packaging. Inspect rough crystal shape with a hand lens. Compare trigonal barrel or tabular forms with isometric dodecahedral, trapezohedral, or rounded garnet forms while allowing for broken or waterworn grains. Rotate translucent rough under neutral white light. Direction-dependent colour can support corundum, but body colour, inclusions, fluorescence, and viewing direction can obscure the effect. Do not scratch a cut or valuable stone. Only on verified expendable rough, compare hardness with appropriate mineral references and confirm a persistent groove rather than loose powder. Use calibrated gemological measurements such as refractive index, optic character, spectrum, specific gravity, and microscopy when trained and when the specimen permits them. Treat fluorescence and inclusions as supporting evidence rather than proof; natural, synthetic, and treated rubies can vary, and some garnets have their own diagnostic spectra or inclusions. For sale, insurance, disclosure, or a consequential identification, obtain an independent report that states identity and any detectable treatment or laboratory growth. Do not scratch, chip, heat, acid-test, or solvent-test jewellery, faceted gems, historic objects, or valuable rough. Home testing can damage surfaces

JavaScript is loading the interactive GeoMiner experience. The identification tools provide educational candidates, not laboratory confirmation.

Ruby vs Garnet: Hardness, Crystal Form and Optical Clues

Continue with related look-alikes

Verification resources