Gemstone profile and identification guide
Ruby is defined by red corundum, but not every red stone carries the same authority of colour. The most sought-after examples combine vivid saturation with enough transparency to let the red remain bright rather than murky.
Ruby is defined by red corundum, but not every red stone carries the same authority of colour. The most sought-after examples combine vivid saturation with enough transparency to let the red remain bright rather than murky.
Did you know? Asterism in star ruby comes from aligned rutile inclusions, which is why that variety is usually cut as a cabochon instead of faceted.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Name: Ruby
Scientific classification: Oxide (Corundum Variety)
Hardness: 9 Mohs
Transparency: transparent
Lustre: vitreous to adamantine
Crystal system: Trigonal
Primary colour: Burgundy
Secondary colour: Red
Colour family: Reds & Pinks
Hardness, strong lustre, and saturated red are central clues. It is often compared with red spinel and garnet, so careful observation of tone, transparency, and any star effect matters when separating the group.
Status: verified-core-fields
Reference priority: GIA, Gem-A, Mindat, International Gem Society
Core identity fields reviewed against consensus gemological references (GIA/Gem-A/Mindat/IGS).
Some market- and locality-level details may still require citation-grade source notes for publication workflows.
Hardness category: very hard
Hardness value: 9 Mohs
Chemical composition: Aluminum oxide (Al2O3) with chromium
Crystal system: Trigonal
Common locations: Mozambique, Myanmar, Madagascar, Tanzania, Thailand
Learn more: Gem-A gemstone education resources.
Ruby sits in the reds & pinks grouping here, usually reading first as burgundy with red appearing as a secondary note or modifier.
Optical effects: Asterism (in star ruby)
Mineral species: Corundum (ruby variety)
Mineral group: Corundum
Chemical formula: Aluminum oxide (Al2O3) with chromium
Mohs hardness: 9
Crystal system: Trigonal
Lustre: vitreous to adamantine
Transparency: transparent
Streak: White
Cleavage: No true cleavage; parting may occur
Fracture: Conchoidal to uneven
Specific gravity: 3.99-4.01
Refractive index: 1.76-1.77
Optical phenomena: Asterism (in star ruby)
Colour range: Burgundy, Red
Common inclusions: Rutile silk, crystal inclusions, and healed fractures
Geological environment: Ruby occurs in Metamorphic marbles and igneous/metamorphic deposits with alluvial concentrations. Its Trigonal structure reflects the pressure-temperature conditions of those host rocks, with notable occurrences in Mozambique, Myanmar, Madagascar, Tanzania, Thailand.
Principal mining regions: Mozambique, Myanmar, Madagascar, Tanzania, Thailand
Important commercial sources: Major modern ruby sources include Mozambique and Myanmar, with additional production from Madagascar and Tanzania
Historical significance: Ruby and sapphire are among the most historically significant and durable gem species.
Common treatments: Heat treatment is common; diffusion and fracture-filling treatments may occur and require disclosure.
Synthetic or imitation forms: Synthetic corundum (Verneuil, flux, hydrothermal) and glass imitations exist.
Common look-alikes: sapphire, spinel, pink sapphire
Jewellery uses: Ruby is used chiefly for Well suited to daily-wear jewellery, especially when cut and set to show colour or brilliance cleanly.. In the trade it is commonly fashioned as faceted stones, calibrated cuts, and higher-clarity collector pieces, with Mohs hardness 9 guiding suitable jewellery applications.
Care recommendations: Ruby should be cleaned with lukewarm water, mild soap, and a soft brush. At Mohs 9 in the Trigonal system, avoid steam cleaners, harsh chemicals, and high-impact wear. Protect cleavage directions from sharp knocks during wear and setting.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Ruby.
Ruby is a Corundum (ruby variety) material with chemistry Aluminum oxide (Al2O3) with chromium. It develops in Metamorphic marbles and igneous/metamorphic deposits with alluvial concentrations, and economically significant production is associated with Mozambique, Myanmar, Madagascar, Tanzania, Thailand.
Major modern ruby sources include Mozambique and Myanmar, with additional production from Madagascar and Tanzania
Best for: Ruby is used chiefly for Well suited to daily-wear jewellery, especially when cut and set to show colour or brilliance cleanly.. In the trade it is commonly fashioned as faceted stones, calibrated cuts, and higher-clarity collector pieces, with Mohs hardness 9 guiding suitable jewellery applications.
Ideal uses: Well suited to daily-wear jewellery, especially when cut and set to show colour or brilliance cleanly.
Ruby should be cleaned with lukewarm water, mild soap, and a soft brush. At Mohs 9 in the Trigonal system, avoid steam cleaners, harsh chemicals, and high-impact wear. Protect cleavage directions from sharp knocks during wear and setting.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Compare hardness (9 Mohs), crystal system (Trigonal), colour profile, and lustre (vitreous to adamantine) with your sample. Then cross-check related gemstones listed above.
Ruby sits in the reds & pinks grouping here, usually reading first as burgundy with red appearing as a secondary note or modifier.
Well suited to daily-wear jewellery, especially when cut and set to show colour or brilliance cleanly.. For maintenance, follow the care guidance in this profile.
GIA: general gemstone identity (reviewed) - Reviewed as a direct core gemstone profile.
Gem-A: gemological education and terminology (reviewed) - Reviewed as a direct core gemstone profile.
Mindat: mineral species and locality index (reviewed) - Reviewed as a direct core gemstone profile.
International Gem Society: collector-facing gem reference (reviewed) - Reviewed as a direct core gemstone profile.
