Corundum (Ruby, Sapphire)

Carat weight is a dominant value driver for fine ruby and sapphire: prices per carat increase exponentially for larger stones with top color and clarity, particularly above 3–5 carats. Commercial-grade smaller stones are more moderately priced, but even here, size combined with attractive color commands premiums.

Color is the key determinant of value. For ruby, pure, vivid red to slightly purplish-red with strong saturation and minimal brown is most prized; for sapphire, velvety royal blue to cornflower blue is the benchmark, with fine padparadscha and other fancy colors also commanding strong prices. Overly dark, overly light or brownish stones are substantially less valuable.

High-value corundum is expected to be eye-clean or nearly so, though some inclusions are accepted in ruby due to its rarity. Obvious cracks, cloudiness or strong inclusions that reduce transparency or durability lower value, while certain inclusions in sapphire can create sought-after effects such as asterism.

Cut quality is critical to maximizing color, brilliance and overall beauty. Well-proportioned mixed cuts, with balanced depth and careful orientation to minimize color zoning, can dramatically enhance value. Poorly cut stones that show windowing, extinction or awkward shapes significantly underperform even with good inherent color.

Corundum is mined in numerous countries including Myanmar, Sri Lanka, Madagascar, Mozambique, Tanzania, Thailand, Cambodia and Australia. Supplies of fine ruby and sapphire are geologically limited and often come from alluvial deposits that are difficult to mechanize, while lower-grade corundum is more abundant.

Demand for ruby and sapphire is consistently strong worldwide, driven by their status as cardinal gems, engagement-ring choices and luxury timepiece staples. Fancy sapphires in pink, yellow and teal hues have gained popularity in contemporary jewelry, broadening the demand beyond traditional blue.

Prices for fine, untreated ruby and sapphire have risen markedly over recent decades, particularly for stones with high clarity and coveted origins such as Burma or Kashmir. Treated commercial materials remain widely available and more affordable, supporting high-volume jewelry lines.