HOW GEMSTONE AUCTIONS WORK

Sotheby's and Christie's are the two dominant houses for major gemstone sales. They have the deepest buyer networks globally and regularly achieve the highest prices for exceptional material. Bonhams is a strong option for mid-range lots ($5,000–$100,000) and has a reputation for accessible entry.

The "hammer price" is what you bid. But it is not what you pay. All auction houses charge a buyer's premium — a percentage fee on top of the hammer price that goes to the auction house. This is the most commonly misunderstood cost for first-time auction buyers.

In practice: if you win a lot at a $50,000 hammer price, your total cost is approximately $63,000–$64,000 after buyer's premium. Budget accordingly — the premium is non-negotiable and is the auction house's primary revenue source.

Additionally, VAT or local taxes may apply depending on jurisdiction. Swiss auction sales (Geneva) typically involve Swiss VAT for buyers taking delivery in Switzerland. Consult with the auction house's client services team before bidding on the tax implications for your specific situation.

The process for registering and bidding at a major auction house is more accessible than many buyers assume:

1. Registration. Create an account on the auction house website. For first-time bidders, the house may request identification documentation and may apply a spending limit. For lots above certain thresholds (typically $10,000–$25,000), they may require a bank reference or deposit. Start this process at least 2 weeks before the sale.

2. View the catalogue. Major sales are published online 4–6 weeks before the sale. Each lot includes: estimate (the range the house expects the lot to sell within), description, condition notes, and certificate details. For major gemstone lots, the full GRS or Gübelin certificate may be reproduced in the catalogue.

3. Request condition reports. For any lot you are serious about, request a condition report from the specialist and, if possible, arrange to view the stone in person during the pre-sale exhibition (typically 2–5 days before the sale). This is standard practice and expected.

4. Set your maximum bid. Know the maximum you will pay — including the buyer's premium — before the auction starts. Auction adrenaline is real and frequently causes buyers to overpay. Set your limit in advance and commit to it.

5. Bidding options: In-room bidding (you attend the sale), telephone bidding (a specialist bids on your behalf by phone — requires advance arrangement), absentee bidding (you submit a maximum bid and the specialist executes up to that limit), or online live bidding (available through house apps for most major sales).

You cannot return the lot. Auction sales are final. Unlike dealer purchases, you generally cannot return a stone after the sale if you change your mind. Due diligence must happen before bidding.

Estimates are marketing tools, not values.Auction estimates are set to generate interest and competitive bidding, not to reflect independent appraisal value. Lots regularly sell above or below estimate.

Competitive dynamics inflate prices.When two or more serious bidders compete, prices can escalate well above fair market value. Know your limit and hold it.

Reserve prices. Most lots have a reserve — a minimum price below which the house will not sell. If a lot does not meet reserve, it passes unsold. The reserve is typically set at or below the low estimate.

Certificate verification. Even at major houses, verify the certificate number online before bidding. Do not assume the house has checked everything — that is your responsibility as buyer.

Auction is the better channel in specific circumstances:

• EXCEPTIONAL, RARE MATERIALThe finest Kashmir sapphires, pigeon blood rubies, and large fine stones are more likely to appear at auction than through dealers, who tend to sell premium material to private clients before listing.
• PRICE TRANSPARENCYAuction results are published and provide genuine price discovery. You know what comparable stones actually sold for.
• SELLER MOTIVATIONEstate sales and motivated consignors at auction may price below what a dealer would charge.
• ACCESS TO CERTIFIED PROVENANCEMajor auction houses curate lot documentation carefully. Top lots come with the best certifications available.

Dealer purchase is often better for mid-range stones, when you need more inspection time, when you want return rights, or when you have an established relationship that provides access to inventory before it reaches auction.