May birthstone
Emerald
The May birthstone is emerald. It is beryl, like aquamarine, but it grows with far more internal fracturing, which is why almost every emerald you will ever see has been oiled to reduce the visibility of those fractures. Emerald reads as 7.5 to 8 on the Mohs scale, but its fracture pattern makes it much more fragile in practice than that number suggests.
- Species
- Beryl colored by chromium or vanadium
- Color range
- Light to deep green, often with a blue cast
- Mohs hardness
- 7.5 to 8
- Also this month
- Nothing else on the modern US list
Inclusions in emerald are normal and expected, and the trade even has a romantic name for them, the jardin. A completely clean emerald of any size should raise a question rather than settle one. What matters is where the inclusions sit and whether any of them reach the surface as an open fracture.
Oiling is a centuries old, accepted treatment. Cedar oil or a modern resin is drawn into surface reaching fractures so they refract light more like the stone around them. It is not permanent, it can dry out over decades, and it can be redone. An antique emerald that looks slightly tired often simply needs re oiling by a specialist.
Because of that fragility, antique emeralds tend to be cut in the rectangular step cut that carries the stone's name, with the corners cut off to protect them, and set in mounts that shield the girdle.
In antique and vintage jewelry
Step cut stones in Edwardian platinum and Art Deco geometry, cabochons in Retro and mid-century gold, and small calibre cut emeralds used as color accents alongside diamonds.
Wearing and caring for it
The one stone where cleaning genuinely matters. Never use an ultrasonic or steam cleaner, and avoid detergents and solvents, all of which strip the oil. Wipe with a barely damp soft cloth. Take an emerald ring off before anything physical.
As a gift
A green that no other stone quite matches. Because the oiling question puts casual buyers off, a properly assessed antique emerald often represents better value than its color suggests.
Common questions
Are all emeralds oiled?
Very nearly all of them, and it has been standard practice for centuries. What we disclose is the fact of the treatment and, where our gemologist can judge it, how extensive it appears to be.
Can an emerald be cleaned in an ultrasonic cleaner?
No. Ultrasonic and steam cleaning can drive out the oil and can worsen existing fractures. A soft cloth and, at most, a barely damp one is the safe limit.
Do inclusions make an emerald less valuable?
Not by default. Emerald is graded on the balance of color and transparency, and a richly colored stone with a visible jardin can be worth far more than a pale, clean one.
Shop the pieces
Shop emerald jewelry
Antique and vintage pieces set with emerald, each one a single example.
Nothing matching this is available right now. Every piece is a single example and sells once, so this changes weekly. Browse everything in stock or ask our buyers to look for it.