About Stienhardt
Third-Generation Diamond House
Built in New York. Cut in House.
Stienhardt is a third-generation diamond company operating out of one of New York\
Our Story
We don\
Every Portuguese, Moval, Dutch Marquise, and Antique Cut starts as a rough stone in our workshop. By the time it leaves our doors, our cutters have spent days on the geometry — facet angles checked against a wheel, pavilions polished by hand, the table positioned to put the fire where the eye lands first.
This is what third-generation means, plainly: the wheel hasn\
Shop In-House Cuts ›Provenance
The wholesale catalog is our catalog.
Our inventory is the same wholesale catalog 3,757 industry buyers see every morning on the MA-DIAM exchange — the system jewelers across New York, Antwerp, and Mumbai use to source their stones. We sell that catalog at our jeweler price plus a thin margin. No mark-up theater, no "designer premium," no story about why a $4,000 diamond suddenly costs $11,000.
If you\
Browse Loose Diamonds ›-
Cut In-HouseSpecialty shapes finished in our New York workshop
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MA-DIAM ProvenanceSame wholesale catalog the trade buys from
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Lifetime Diamond UpgradeTrade up at any time, full value credit
What We Sell
Three categories, one standard. Choose what suits the moment.
What Customers Say
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"They cut the Portuguese for me from a rough stone. Spent two weeks on it. Nobody else in the diamond district even quoted the job."
— — Maya R., New York -
"My grandfather bought a ring from Stienhardt in 1962. Three generations later, I bought my wife\'s engagement ring at the same counter."
— — David L., Queens -
"Showed me their wholesale screen. Same exact stone three other jewelers were quoting at almost double."
— — Daniel K., Los Angeles
Frequently Asked
What does MA-DIAM provenance mean?
MA-DIAM is the wholesale diamond exchange jewelers across New York, Antwerp, and Mumbai use to source their stones — currently 3,757 industry buyers. Every diamond on Stienhardt.com traces back to that catalog, with the cutter, supplier, and certification path on file. We don\'t buy from middlemen.
Are your diamonds certified?
Every center stone over 0.50 ct ships with a GIA or IGI report. Smaller accent stones are graded in-house against the same scales — we\'ll send you the worksheet on request. We don\'t use EGL, AGS-non-laboratory, or any in-house "certificate" as primary documentation.
Where do your natural diamonds come from? Are they conflict-free?
Yes. Our natural stones come exclusively from Kimberley-Process member countries — primarily Botswana, Namibia, South Africa, and Canada. We do not source from Russia or any post-2022 Russian-origin trade. The Chain of Custody documentation ships with every natural diamond.
Can you make custom pieces? What does that take?
Most of our work is custom. Bring a Pinterest board, a photo of an heirloom, or a rough idea — we CAD-design in-house, render in 3D for approval, then produce in our New York workshop. Standard custom takes 3–4 weeks; an in-house specialty cut adds another 1–2 weeks because the rough has to be sourced and cut to spec.
Tell me about the family.
Three generations in the diamond business, working out of the same New York address since the 1940s. We don\'t put founder portraits on the homepage — most of our work is referrals from previous customers and from other jewelers. If you visit the counter, you\'ll meet the cutters and the family.
Three Generations, One Counter
Visit the Workshop
In-person at the New York counter or by video. We\