Ruby

Color is almost the whole story

With ruby, color outweighs every other factor. A one-carat stone of exceptional red can be worth many times a larger one that reads brownish or overly purple.

The benchmark is pigeon’s blood: a pure, vivid red with the faintest blue undertone, medium to medium-dark in tone, historically associated with Burmese material. It is a trade term rather than a precise grade, so treat it as a description to verify with your own eyes, not a guarantee.

• Too purple and the stone reads cool and loses value, though a slight blue secondary is desirable.
• Too orange or brown and it drifts toward garnet territory in appearance, which the market prices accordingly.
• Too light and it may be classified and priced as pink sapphire instead.
• Too dark and it goes flat and lifeless in anything but bright light.

Many fine rubies also fluoresce under ultraviolet light, including the UV in daylight, which makes the red appear to glow from within. Burmese stones are particularly known for it, and iron content in material from some other sources damps the effect.

Clarity: expect inclusions

Rubies are almost always included. A flawless natural ruby of any size is so unusual that a stone presented as one, at an ordinary price, is more likely synthetic or treated than a lucky find.

Fine silk, microscopic rutile needles, is normal and in the right quantity actually improves the stone, softening the light and spreading color. What matters is whether inclusions are visible enough to disturb the eye or sit where they threaten the stone’s durability.

Why fine ruby costs what it does

At the top of the market, ruby is the most expensive gemstone in the world per carat, ahead of diamond. Three things drive it:

1. Genuine scarcity in larger sizes. Fine rubies above a few carats are extraordinarily rare, so price per carat climbs steeply with size rather than proportionally.
2. Untreated stones command a large premium. Most rubies on the market are heat-treated, which is accepted and permanent. Some are lead-glass filled: a far more invasive treatment that fills fractures, can be damaged by ordinary jewelry repair, and is worth a small fraction of an equivalent heated stone.
3. Origin is priced. Burmese (Myanmar) material carries the strongest premium; Mozambique has become a major modern source of excellent stones at more accessible prices. Note that sanctions have periodically restricted Burmese ruby imports into the United States, so ask about provenance documentation.

Living with a ruby

At 9 on the Mohs scale, ruby is as scratch-resistant as sapphire and among the most practical colored stones for a ring worn daily.

To judge red against red with more precision, read our gemstone color guide.