Emerald

Emerald is the green variety of beryl, coloured by chromium or vanadium, Mohs hardness 7.5–8 — the most delicate of the three great coloured gemstones. It is usually included (the trade calls this the jardin, or garden) and tender by nature; oiling has been standard practice for over a century, and a perfectly clean emerald is, in fact, suspect. It is May’s birthstone.

About Emerald

Emerald is beryl (a beryllium aluminium silicate), turned green by chromium or vanadium, Mohs hardness 7.5–8 — the most delicate of the three great coloured gemstones. It shares its family with aquamarine. That green — deep, saturated, alive — is one no other stone quite imitates.

Why Choose an Emerald

Emerald is May’s birthstone, and its deep green is one of a kind; its inclusions are its signature, the trade’s jardin, or “garden”. Since antiquity it has been the stone of emperors and nobility, carrying a classical, stately air. A wholly clean emerald is, paradoxically, suspect — too clean, and it may be synthetic.

History & Famous Stones

Emerald has been the stone of emperors and nobility since antiquity — from Cleopatra’s mines in ancient Egypt to Colombia’s Muzo and Chivor today, that deep green has always been the colour of power and legend. A few great emeralds tell the whole story of the stone’s weight:

• The Rockefeller Emerald: 18.04 carats, a Colombian emerald sold in 2017 for about US$5.5 million — a record price per carat for an emerald.
• The Duke of Devonshire Emerald: 1,383.93 carats uncut, from Colombia’s famed Muzo mines, considered priceless and now in the Natural History Museum in London.
• The Patricia Emerald: 632 carats, a natural crystal found in Colombia in 1920, rarely kept in its original twelve-sided crystal form, now at the American Museum of Natural History.

The Truth About Emerald

Oiling is a century-old norm (the amount must be declared); “too clean” is suspect (possibly synthetic); it is delicate, and never for ultrasonic.

• Truth one: oiling is a century-old norm. Cedar oil is worked into the fractures to make the stone appear clearer; declared honestly and light in amount, it is normal trade.
• Truth two: the oil grade moves the value greatly. A certificate notes the amount (none / minor / moderate / significant) — if you cannot read that line, do not rush to pay.
• Truth three: “too clean” is suspect. Synthetic emerald is a mature technology and hard to spot by eye; rely on a certificate.
• Truth four: it is delicate by nature, not by fault — accept its tenderness, and it will stay with you.

Emerald on the Market

Tell apart natural (declared oiling), resin-filled, synthetic and dyed-and-injected; it comes down to the oil grade and whether it is synthetic.

Type	Traits	Price	How to tell
Natural · declared oiling	Garden inclusions, cedar oil	High	Certificate grades the oil
Resin-filled	Synthetic resin in fractures	Low–mid	Resin ages and discolours
Synthetic emerald	Too clean, too perfect	Low	Certificate, inclusion traits
Dyed, injected poor rough	Low-grade rough dyed green	Low	Dye pools in the fractures

Before You Buy

An emerald must not meet ultrasonic or steam (they drive out the oil); check the oil grade and whether it is synthetic; clean only with warm water and a soft cloth.

• An emerald must never go in ultrasonic or steam cleaning — it drives out the oil and opens the fractures.
• Read the oil grade and whether it is synthetic; these two set its worth.
• Avoid knocks and sudden temperature change; it is far more delicate than the corundum family.
• What you buy is that green and that garden — accept its tenderness, and it will last.