Small vault. Honest stones.
Harlow Mercantile is an online-only boutique. We keep the Vault intentionally small so that every stone listed has been chosen individually, inspected by hand, and honestly represented. Every diamond ships with its own IGI grading report.
Seven steps, one stone.
- 01
Grown, not mined
Every Harlow diamond begins as a small seed placed in a controlled chamber. Over several weeks it grows into a rough crystal that is chemically and optically identical to a mined diamond, with a clearer origin story.
- 02
The rough is studied
Before a single facet is cut, the rough is scanned and mapped. Cutters plan the shape that will honour the crystal, balancing size against the brilliance the finished stone can hold.
- 03
Cut for light, not weight
Master cutters work the rough by hand, choosing the proportions that return the most light. We favour cut quality over holding on to extra carats that would dull the finished stone.
- 04
Polished by hand
Each facet is polished individually until the surface reads clean under a loupe. This is slow work. It is the difference between a stone that looks fine and one that looks alive.
- 05
IGI certified
Every diamond is sent to the International Gemological Institute for independent grading. The finished report covers cut, colour, clarity, carat, measurements, and confirms the stone as laboratory grown.
- 06
Reviewed by Harlow
Only a small number of stones make it into the Vault. We look past the paper report and study each diamond in person for brightness, character, and how it holds light in ordinary daylight, not just under a jeweller's lamp.
- 07
Ready for its setting
The stone is given a Vault number, photographed, and listed with its full IGI report. From there it waits for the person who will design its setting, whether that is with their own jeweller or through a future Harlow collection.
What earns a spot in the Vault.
A grading report is a starting point. It is not the whole story. Before a stone is listed we hold it, turn it, and ask a simple question. Would we be proud to give this to someone we love.
Cut first
Cut is the single biggest driver of how a diamond looks in real life. A well cut stone at a modest colour grade will out-sparkle a poorly cut one on paper every time. We start there and work outward.
Eye clean at arm's length
We do not chase flawless grades. We look for stones that read clean to the eye at normal viewing distance, so the value goes into brilliance rather than a certificate line.
Colour that flatters skin
For colourless diamonds we favour the D to G range. For fancy shapes we accept a touch more warmth when it makes the stone feel more alive rather than icy.
Character over volume
We would rather list one stone with real presence than ten average ones. The Vault grows slowly on purpose.
An online-only boutique with a small, curated Vault.
Harlow Mercantile is an online-only boutique for premium lab-grown loose diamonds. We do not operate a showroom and we do not list hundreds of stones. The Vault is intentionally small, because we would rather offer a few diamonds we truly believe in than a catalogue that feels like a lottery.
Each diamond in the Vault is chosen one at a time, photographed as it is, and listed with its own IGI grading report. No stone is borrowed, stock, or shown as a stand-in. What you see is the exact stone that will arrive.
If you have a question, send us a note. A real person will reply, usually within one business day.
What we promise.
Six promises we keep, from the diamond itself to the box it arrives in.
IGI Certified
Every diamond ships with its full IGI grading report.
Ethically Lab-Grown
Chemically identical to mined stones, with a clearer origin.
Secure Shipping
Every order ships securely with tracking included.
Honest Pricing
Fair prices on every stone. No pressure, no upsell.
Real Support
Questions go to a real person, with replies within one business day.
Signature Packaging
Each stone arrives ready to gift, hold, or set.
Custom fine jewelry is coming.
Engagement rings, earrings, pendants, and necklaces are future plans. Join the Vault List and we’ll let you know when they arrive.
See what made the cut.
The Vault is small on purpose. Each stone is one of one, chosen individually and photographed as it is. Every diamond is listed with its own IGI grading report.