Colombian Emerald Buying Guide

Why Colombian emeralds are special

Colombia has been the benchmark for emeralds for nearly five centuries. Emeralds were traded and worn in the region long before the Spanish arrived. Spanish forces reached what became the Chivor (Somondoco) workings in 1537, and Spanish mining at Muzo began in 1567 [3]. Many of the most celebrated emeralds in royal and museum collections are Colombian.

What makes Colombian stones different is geology. Most of the world’s emeralds form where chromium-bearing rocks meet granitic intrusions (often called “schist-type” deposits). Colombian emeralds instead crystallised from hot, salty fluids that forced their way through fractured black shale, forming calcite-rich veins [3][4]. This low-iron environment is one reason fine Colombian stones can show such a pure, bright green.

The mines: Muzo, Coscuez, Chivor and beyond

Colombia’s emerald deposits lie in two narrow belts on either side of the Eastern Cordillera of the Andes, in the departments of Boyacá and Cundinamarca [6].

Be careful with mine names. In the trade, “Muzo” and “Chivor” are often used to describe a colour style rather than a proven mine [6]. Even GIA notes that the appearance of emeralds from different sources overlaps [1]. Laboratories normally report the country of origin, not the mine. Treat a specific mine claim as a story unless it’s backed by documented provenance.

Want to go deeper? Our three-part series covers Colombia’s emerald history, the Western belt and Muzo and Coscuez.

Colour, clarity, cut and carat

There is no universal grading scale for emeralds like there is for diamonds, but the trade judges them on the same four factors, in roughly this order of importance.

Emerald oil treatment explained

Because of how they form, emeralds almost always contain fissures. Filling surface-reaching fissures with a colourless substance makes them much less visible, so the stone looks cleaner and brighter. This is called clarity enhancement (or “oiling”). It’s an accepted, centuries-old practice, but it must be disclosed [2].

What goes into the fissures?

How labs grade the amount of treatment

The leading laboratories have agreed a common approach through the Laboratory Manual Harmonisation Committee (LMHC). It grades the amount of filler from none, through minor (F1) and moderate (F2), to significant (F3), and stresses that clarity enhancement is usually reversible and repeatable, so a report describes the stone only at the time of testing [8].

Rarer and more valuable on the left, more common and less valuable on the right.

How much does treatment affect value?

For two stones of the same colour and size, the less filler the better. In practice:

• None / insignificant: the rarest and most expensive. Collectors pay a substantial premium.
• Minor (F1): the most popular choice for fine jewellery. The stone looks much the same with or without its filler.
• Moderate (F2): acceptable at the right price, but the filler is doing visible work.
• Significant (F3): the filler is hiding a lot. Should be priced accordingly, and needs extra care in wear.

GIA’s research found the degree of enhancement depends on the size, number and position of filled fissures, especially those under the table [10]. A small amount of oil in a large fissure under the table can matter more than more oil near the edge.

The best certification for emeralds

An independent report is the single best protection when buying an emerald. A good report confirms the stone is natural emerald, grades the clarity enhancement and names the filler, and gives an origin opinion. These are the laboratories most respected for emeralds:

Which report should you want?

• Under about £2,000: a reputable local or gemmologist report is reasonable.
• £2,000 to £20,000: look for GRS, GIA, SSEF, Gübelin or AGL, stating natural emerald, treatment level and origin.
• Investment or collector stones: SSEF or Gübelin (sometimes both) is the norm at auction level.

Always check that the report number, weight and measurements match the stone, and verify the report online where possible.

What do “Muzo Green” and “Old Mine” mean?

GRS issues an “Old Mine / Muzo Green” appendix for emeralds whose colour falls within its top green bands: intense to vivid, vivid, and vivid to deep green. The current system has been in use since late 2017 [11].

It’s important to understand what it is and isn’t:

• It’s a colour term, describing a colour reminiscent of classic old-mine Colombian emeralds.
• It is not proof that a stone came from the Muzo mine. Origin is stated separately on the report.
• Other labs such as SSEF use descriptive colour terms only, with no trade names [2].

A GRS “Muzo Green” appendix on a stone that also has Colombian origin and minor treatment is a strong combination. Several of our current emeralds carry it.

Colombian vs Zambian vs Brazilian emeralds

These are tendencies, not rules. GIA notes that the appearance of emeralds from different sources overlaps [1], so origin can only be confirmed by a laboratory. Buy the stone you love, and pay the origin premium only when a report supports it.

Synthetic emeralds, imitations and red flags

Laboratory-grown (synthetic) emeralds have the same chemistry as natural ones and are made by flux or hydrothermal growth. They can look very convincing, and are separated from natural stones by their inclusions and by spectroscopy [12]. Imitations include green glass, doublets and other green stones.

How much does a Colombian emerald cost?

Emerald prices vary more than almost any other gem. Two 2-carat stones can differ in price many times over. The main drivers, roughly in order, are:

1. Colour: hue, saturation and tone.
2. Treatment level: none and insignificant command a premium, then minor, moderate and significant.
3. Transparency and clarity: a bright, “crystalline” stone is worth far more than a cloudy one.
4. Size: price per carat rises steeply with weight [1].
5. Origin and report: Colombian origin from a top lab adds value.
6. Cut: good proportions and a lively face-up appearance.

For reference, our current certified Colombian emeralds of about 0.6 to 2.8 carats are priced from around £6,800 to £24,500, depending on colour, treatment and report. See current prices. If you have a budget in mind, tell us and we’ll show you what it can buy.

Setting and caring for your emerald