gemstone
Ruby (Corundum)
Aluminium oxide with chromium (Al₂O₃:Cr)
AI-generated identification · may be incorrectMohs hardness 9; deep red to pigeon-blood red; vitreous to adamantine luster; trigonal crystal system; specific gravity 3.97–4.05.
Identified More gemstone →
Explore Ruby (Corundum) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness 9; deep red to pigeon-blood red; vitreous to adamantine luster; trigonal crystal system; specific gravity 3.97–4.05.
Formation & geological history
Formed in regional metamorphic rocks such as marble or mica schist, and in silica-poor igneous rocks like pegmatites and nepheline syenites.
Uses & applications
Prized as a high-end precious gemstone in jewelry, and historically used in horology (watch bearings) and early laser technology.
Geological facts
Red corundum is exclusively called ruby, while all other colored gem-quality corundum varieties are classified as sapphires. It fluoresces strongly under UV light.
Field identification & locations
Identified by extreme hardness (scratches quartz and topaz), high density, strong red pleochroism, and often hexagonal crystal habits; notable sources include Myanmar, Mozambique, and Sri Lanka.
More like this
Other gemstone specimens
Ammolite
Ammolite (Biogenic Aragonite with trace elements; fossils of Placenticeras meeki and Placenticeras intercalare)
mineral
Gemstone Ring
N/A - Set piece of jewelry, likely Amethyst or Garnet with Diamond or CZ
gemstone
Amber
Succinite (Organic Gemstone)
mineral
Diamond and Gold Jewelry
Carbon (Diamond) / Au (Gold)
gemstone
Red Jasper
Silicon Dioxide (SiO2) with Hematite inclusions
sedimentary
Cubic Zirconia (simulant) or Diamond
ZrO2 (Cubic Zirconia) or C (Diamond)
gemstone