A different way for retailer jewelers and dealers to buy & sell diamonds

Harmony Diamond Auctions are online diamond auctions for the trade, featuring loose or mounted diamonds, 0.40 carats and up.

Retailers, pawn brokers and dealers alike benefit from an additional revenue stream by selling secondary market goods or flipping out of older inventory. Buyers – qualified and vetted members of the trade – get great deals.

Items are sent to Hoover & Strong, and independently inspected, graded and photographed. All items include detailed descriptions, grading, images, 3D photos, and cert info.

Buyers bid and are notified if they are the highest bidder on the item. At the close of the auction, sellers are presented with the highest bids and can accept or reject the offers.

Auctions run every 2 weeks, Monday – Wednesday. Final payments to sellers are processed within the same week.

All Polygon members are pre-approved to participate, and can access auctions on the Polygon member platform.


  • + Neutral & Private
    Anonymity of buyers & sellers, secure transactions
  • + Transparent
    Independent grading & full descriptions, transparent process
  • + Personalized Support
    Dedicated auction team available to talk, or chat online
  • + Quick Timeframe
    2-day auctions, with completed transactions & payments same week

How it Works

  • Open to Polygon members and qualified members of the trade
  • + Sellers ship goods to Hoover & Strong.
  • + Certified gemologists inspect and grade the diamonds, photograph the goods and upload them to the auction.
  • + The 2-day auction opens on a Monday. Buyers bid on items.
  • + The auction closes and sellers are presented with the highest bids. Sellers can accept or reject offers, or counter-offer.
  • + Buyers are notified of accepted bids and invoiced for items won. Goods are shipped to the buyers, who have 24 hours to inspect the items. Items cannot be rejected unless they were not as described.
  • + Sellers get paid!

Commonly asked questions

How frequent are the auctions, and how long do they last?

Auctions are held twice a month, starting on the first and third Monday of every month. Auctions will normally begin Monday of every week at 12:00pm EST and will end on Wednesday at 2:00pm EST.

What type of diamonds will be featured in the auctions?

Single diamonds from 0.40ct and diamond parcels of sizes +0.20ct (+17 sieve). Diamonds can be loose or mounted.

Are there fees to participate in the auctions?

Auctions fees only apply if a sale is accepted, with the exception of optional auction features purchased during the auction and shipping fees.

How do you grade the diamonds?

Grading will be done according to strict GIA standards. Detailed descriptions, as well as several high resolutions images, will be available for each diamond listed for auction.

How do I become a seller or buyer?

Polygon members are pre-qualified to enroll using our expedited registration process. Otherwise, click the “Apply” button and fill in the form. Registrations are reviewed to ensure you are part of a valid jewelry business, and you comply with AML and other application requirements.

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Contact Polygon for More Info

Not sure how auctions work or in need of more information? Our customer support specialists are available to answer any questions you may have about our service!

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