Episode 03 — The Gemmacol Podcast
What actually makes a green stone an emerald? Why does a tsavorite or a green spinel sometimes pass for one at first glance? And how do you tell a natural Colombian emerald from a synthetic, a doublet, or a piece of green glass?
In this episode, we look at the green stones that sit next to emerald in the market — the lookalikes, the imitations, and the laboratory-grown material — and explain what actually separates them. Colour gets a buyer’s attention. Identification protects their money.
What Makes an Emerald an Emerald
Emerald is the green variety of beryl, a mineral composed of beryllium, aluminium, silicon, and oxygen. Its identity rests on two things: the cause of the colour and its intensity. In emerald, the green is produced by chromium and/or vanadium in the crystal lattice — the trace elements responsible for the saturated, slightly bluish green that defines the finest Colombian material.
Laboratories also apply a saturation threshold: a stone must reach a sufficient depth of tone and saturation to be called emerald. This is why two stones described as “emerald” by different sellers can carry very different values — and why the laboratory’s wording on the certificate matters.
The Green Lookalikes — Natural Stones Mistaken for Emerald
Several natural gemstones share emerald’s colour but belong to entirely different mineral species. Each is a legitimate gem in its own right — the problem only arises when one is sold, or bought, as the other.
| Gemstone | Mineral Species | Colour Agent | Hardness (Mohs) | Key Distinction |
|---|---|---|---|---|
| Emerald | Beryl | Chromium / Vanadium | 7.5 – 8 | Jardin; three-phase inclusions in Colombian material |
| Tsavorite | Grossular garnet | Vanadium / Chromium | 7 – 7.5 | Singly refractive; higher brilliance, rarely large |
| Green Spinel | Spinel | Iron (rarely Chromium / Vanadium) | 8 | Singly refractive; synthetic spinel long used as a simulant |
| Green Tourmaline | Elbaite tourmaline | Iron (Cr/V in “chrome” variety) | 7 – 7.5 | Strong pleochroism; darker along the length |
| Peridot | Forsterite olivine | Iron | 6.5 – 7 | Olive-yellow green; visible facet doubling |
| Green Sapphire | Corundum | Iron | 9 | Muted, often bluish or yellowish green |
Chromium and vanadium colour tsavorite as well as emerald, while iron produces green in tourmaline, peridot, sapphire and spinel. Unrelated minerals arrive at the same colour by different routes — which is exactly why colour alone can never identify an emerald.
Synthetics, Composites and Imitations
Beyond natural lookalikes, the market contains material made to look like emerald — or made to be emerald in a laboratory. These fall into three categories, and each requires disclosure by law in most European jurisdictions.
Laboratory-grown emerald has the same chemistry and crystal structure as natural emerald. It is produced by flux or hydrothermal growth in weeks rather than millions of years. The difference is in the growth signature: flux veils, chevron or wavy growth patterns, and platinum platelets from the growth vessel — features a trained gemmologist or laboratory can detect, but the naked eye usually cannot.
Assembled stones join two or three pieces — often colourless or pale beryl, quartz, or low-grade emerald — with a green cement or layer between them. Viewed face-up and mounted in a closed setting, they can be convincing. Viewed from the side, or immersed in liquid, the join line and the colour concentrated in a single plane give them away.
Green glass is the oldest emerald imitation. It is singly refractive, softer, warmer to the touch, and typically shows round gas bubbles and swirl marks rather than the angular, multi-phase inclusions of a natural stone. Inexpensive to produce — and still common in tourist markets and undocumented online listings.
How a Gemmologist Tells Them Apart
Identification is a process of elimination. No single test is conclusive on its own; a professional combines several readings before reaching a conclusion.
Emerald reads at approximately 1.57–1.58 with low birefringence. Tsavorite, spinel, peridot, tourmaline and sapphire each fall in different ranges — a refractometer separates most natural lookalikes in seconds.
Under magnification, the jardin tells the stone’s story. Colombian emeralds typically show three-phase inclusions — a liquid cavity containing a gas bubble and a salt crystal. Synthetics show growth-related features; glass shows bubbles and swirls.
Chromium-rich, low-iron emeralds — typical of Colombia — often appear red or pink through a Chelsea filter. A useful indicator, but not proof: some synthetics and other chromium-coloured stones react the same way.
Spectroscopy and trace-element analysis confirm species, natural versus synthetic origin, geographic origin, and treatment. This is the step that turns an opinion into a documented fact.
Never buy a green stone on colour alone. Ask for a certificate that states three things explicitly: the species (emerald), natural origin, and the treatment designation. If any one of the three is missing, the stone has not been fully identified.
Gemmacol supplies certified Colombian emeralds — Muzo, Chivor & Coscuez origin — directly to jewellers, designers, and auction houses across Europe. All stones ship with full GIC origin and quality documentation.
Trade enquiries: info@gemmacol.com
