The stones · III
Emerald
Green beryl, coloured by chromium and vanadium, and the one stone where I make an exception to my rule — a narrow one.
What I buy
Emerald grows fractured; the crystal is the price of the colour. Nearly every emerald in the world has had its fissures filled with oil, and the laboratories grade how much: none, insignificant, minor, moderate, significant. I buy Colombian and Zambian emerald at insignificant or minor only, with a report from Gübelin, SSEF or AGL that also names the filler. Cedar oil is traditional and reversible. Resin is neither, and I do not buy it at any grade.
Colombia — Muzo, Coscuez, Chivor — remains the reference for the warm, slightly bluish green with the soft crystal that no other origin repeats. Zambia, from the Kafubu belt, gives a cooler, bluer green in cleaner crystal, and the best Zambian stones are now bought by people who know exactly what they are looking at. I work both.
A collection emerald is a stone whose green is saturated without grey or black, whose crystal is transparent enough to look into, and whose garden of inclusions reads as character rather than damage. Size counts less than it does for ruby; colour and crystal count more.
How I judge it
- Colour first, in daylight: a green that is alive, not olive, not grey, not black at the edges.
- Crystal: look into the stone, not at it. The finest emeralds have depth you can fall into.
- The garden under the loupe: three-phase inclusions are the signature of Colombia; a good garden is not a flaw.
- The flash test: filled fissures show an orange or blue flash under the loupe. Oil flashes lightly; resin does not stop.
- Never ultrasonic, never steam, never heat. The stone is handed over with instructions.
- The report: origin, filler type, and the degree of clarity enhancement, in one line, from one of three laboratories.
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Questions collectors ask
Why do you accept oil in emerald when you refuse heat in ruby?
Because an untreated emerald of fine colour barely exists; the crystal grows fractured. Traditional oil at insignificant or minor grade is reversible and declared on the report. Resin and higher grades are neither, and I refuse them.
Colombia or Zambia?
Colombia for the classic warm green and the soft crystal; Zambia for a cooler green in cleaner crystal at a fairer price. Both are bought on the same laboratory grades, and both belong in a serious collection.
How should an emerald be cared for?
Wiped with a soft cloth and nothing else. No ultrasonic cleaner, no steam, no heat, no solvents: any of them can draw the oil out of the fissures and change what you see.
