The expert behind Johya
Vincent Renault, gemologist
Vincent Renault, who has always been passionate about gemology and holds a degree in the field, is the co-founder of Johya alongside his business partner Dimitri Velasco.
His role is very hands-on: he travels to Colombia, to the Boyacá region, selects the stones himself, negotiates directly with the sellers, and then tracks each emerald until it is certified by an independent laboratory.
A degree—and, above all, a method
A degree in gemology isn’t just for show. It provides the vocabulary, the tools, and the skills needed to describe a stone without embellishing it—and, when necessary, to reject it. An emerald is examined under a 10× magnifying glass, under a lamp, and on a scale; it doesn’t tell its own story.
Every stone in the catalog has passed through Vincent’s hands before arriving here: examined under a magnifying glass and a UV light, weighed at various stages, and photographed without any retouching. Nothing is computer-generated or “enhanced”: what is shown on the product page is exactly what the customer will receive.
What he sees in an emerald
First, the color. An emerald is a type of beryl that owes its green color to chromium and vanadium. This is the factor that carries the most weight in determining its value: its vibrancy, its saturation, and how it holds up under different lighting conditions.
Next, the “garden.” The inclusions in an emerald are not flaws to be hidden: they are its fingerprints. A perfectly pure emerald should arouse suspicion rather than charm. The key is not their absence, but their nature and location.
Finally, size and weight. A good cut enhances the stone’s color and durability—the emerald is hard but fragile. Weight alone is never a reliable indicator: two identical carats can be worth ten times less than one another.
On the ground in Colombia
Purchases are made on site, in the emerald-rich region of Boyacá. The real work involves less the folklore of the markets and more patience: looking at a lot of stones, setting aside the vast majority, coming back, and buying only what stands up to scrutiny once you’re back home.
This on-site presence makes it possible to document a stone’s journey—with photos taken at the time of purchase, during cutting, and after it has been cut—and to publish that information. This is what Johya calls its traceability: not a promise, but a record that can be consulted stone by stone.
What He'll Never Say
That a stone comes from a specific mine, without proof. Buying an emerald in Muzo does not prove that it was mined there: the place of purchase is not the mine. Only an independent laboratory can certify a stone’s origin, and it certifies a country—rarely a specific mine. When Johya writes “Colombia,” that is what the certificate says.
That an emerald has not undergone any treatment, for convenience. Virtually all emeralds on the market are oiled: this is an ancient gem-cutting practice that is accepted and exempt from the “treated” designation. Johya goes a step further and specifies the observed degree of treatment—none, minor, or moderate. A stone containing resin, on the other hand, is subject to a treatment that must be disclosed: it is labeled as such.
This approach is not a marketing ploy: it is the only way to remain accurate. We do not make claims about anything that cannot be verified.
The Field Notebook
Purchasing trips are documented as they unfold: routes, emerald markets, cutting workshops, and meetings with sellers.
