What is Ruby?
Ruby is the red gem variety of corundum, one of the world's most important coloured gemstones and a high-value collector material.
Mineralogy and crystal structure
Reference formula: Al2O3. Ruby is corundum coloured mainly by chromium and sometimes iron. The selected structure is a clearly labelled representative corundum model: Ruby is a variety, not a separate ideal species. Heat treatment, fracture filling and origin can strongly affect value. Ruby is classified with oxides and has a trigonal crystal system. Typical hardness is 9–9 on the Mohs scale and specific gravity is approximately 3.9–4.1.
Colour, lustre and habit
Typical colours include vivid red, purplish red, pink-red. The usual rhombohedral, tabular, granular habit and vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Ruby forms in or is associated with aluminium-rich metamorphic rocks, marble, basaltic rocks and alluvial gem deposits. Important documented localities include Myanmar, Mozambique, Sri Lanka, Vietnam, Thailand, Tanzania and documented ruby districts worldwide.
The red benchmark of the gem market
Ruby combines scientific simplicity with exceptional commercial importance: a corundum lattice can host trace chromium that turns a common oxide framework into a globally recognised gem. Treatment disclosure and independent verification are part of responsible buying.
Collecting and care
Protect from sharp impact and sudden thermal change. Warm soapy water is generally safe, but fracture-filled or cavity-filled stones should be cleaned only with a damp cloth and valuable stones should retain their laboratory report.
