Choose a wholesale diamond supplier on six things: independent certification, clear natural and lab-grown disclosure, documented conflict-free sourcing, real stock depth across shapes and sizes, transparent trade terms, and fully insured delivery. Test the relationship with a single stone or a small order before you commit to regular supply.
1. Independent certification, not house grading
Ask which laboratory issues the grading reports. An independent report from a recognised laboratory is the only description of a stone that a third party will accept, and it is what lets you price and describe the diamond to your own customer with confidence. A supplier who grades their own stones without independent verification is asking you to take their word for the most valuable part of the purchase.
2. Natural and lab-grown clearly separated
A supplier must be able to tell you, in writing, whether a stone is natural or laboratory-grown, and the certificate should say so. Ambiguity here is not a paperwork problem; it is a legal and reputational risk, because selling a lab-grown stone as natural is not permissible. Check that the separation is built into their records and their labelling rather than left to a conversation.
3. Documented, conflict-free sourcing
Natural diamonds should comply with the Kimberley Process Certification Scheme, which exists to keep conflict diamonds out of legitimate supply. Beyond compliance, ask whether provenance and inscription details are available for the stones you buy. A supplier who can produce that documentation on request is one whose goods you can describe accurately and defend if challenged.
4. Stock depth that matches what you sell
Depth matters more than breadth. You need the shapes you actually sell, in the grades your customers buy, with matched pairs for three-stone and shoulder settings and calibrated parcels for pave work. A supplier with a deep position in round brilliants but no fancy shapes may not suit a business built on ovals and emeralds. Ask how quickly they can source a stone they do not hold, because that is the test most suppliers eventually fail.
5. Trade terms you can plan around
Ask what the pricing basis is, whether minimums are hard or flexible, what the payment schedule looks like, and whether memo or consignment is available. Get the terms in writing before the first order. The cheapest quote is not the best supplier if it comes with a deposit structure or a lead time that does not fit how you sell. What is a diamond trade account? explains how accounts and terms usually work.
6. Insured delivery and retained documentation
Diamonds should be insured for their full replacement value in transit, tracked, and covered until signed for, with collection by appointment as an option. Just as important is what happens afterwards: certificates, provenance and order records should be retained so that a question about a stone two years later can be answered from the file rather than from memory.
A seventh point: can they make as well as supply?
If you sell bespoke or own-brand work, a supplier who can also manufacture removes a handover from your process. A diamond house with its own workshop can source the stone and make the piece, which means one set of records, one point of accountability and one place to track progress. Bespoke jewellery manufacturing and white label manufacturing are the services to look for.
Testing a new supplier
Do not test a supplier with your most important order. Start with a single stone or a small commission, and judge the things that matter over time: how quickly a shortlist arrives, whether the stone matches the certificate, whether the paperwork is complete, how problems are handled, and whether the second order matches the first. If a supplier passes that, scale the relationship. Contact Caesar Diamonds to start with a shortlist or a trade account application.