Buying Estate Jewelry at Auction: 9 Checks Before You Bid

1. Read the metal line, then ask how it was tested

Common marks include 14K or 585, 18K or 750, PT950 or PLAT for platinum, and 925 for sterling silver. Marks are helpful but not proof. They can be worn, added later or simply wrong. Ask whether the auction house tested the metal (acid, electronic tester or XRF) or is simply reporting the stamp. “Tests 14K” and “stamped 14K” are different statements.

2. Natural, lab-grown or simulant?

Three very different things can look alike:

• Natural: formed in the earth.
• Laboratory-grown (synthetic): the same material as the natural stone, created in a lab. Real diamond or real sapphire, but a different market value.
• Simulant: looks similar but is a different material, such as cubic zirconia or moissanite imitating diamond, or glass imitating emerald.

If the description just says “diamond” or “ruby,” ask whether it has been identified as natural, and by whom.

3. Treatments: what has been done to the stone?

Many gemstones are routinely treated. Common examples include heating of sapphires and rubies, oiling or resin-filling of emeralds, and fracture-filling or coating of some diamonds. Treatment is not necessarily a problem, but it affects value and care, and it should be disclosed. Ask: “Is the stone treated, and is that stated on a lab report?”

4. Is there a lab report, and can you verify it?

For significant stones, look for a report from an independent gemological laboratory. Major labs, such as GIA, let you check a report number on their own website. Confirm that the weight, measurements and any laser inscription on the girdle match the stone in the lot. A report describes a stone, not a ring, so make sure it is the same stone. An appraisal document with a “retail replacement value” is not a lab report and is not a market price.

5. Understand the weight numbers

“TCW” or “total carat weight” adds up every stone in the piece. A ring described as “2.00 ctw” might have a 1.00-carat center and many small accent stones, which is valued very differently from a single 2-carat stone. Ask for the center stone’s weight separately, and whether it was weighed loose or estimated while mounted.

6. Inspect the condition you can’t see in photos

Ask for close-ups or a condition report covering:

• prongs: worn, thin or rebuilt;
• shank: thinning or cracks on rings that have been worn for years;
• solder marks: from past resizing;
• chips on stone edges;
• missing accent stones;
• worn enamel;
• clasps and safety catches.

Budget for any repair the piece needs before it can be worn safely.

7. Signed pieces need a maker’s mark and documentation

A piece described as “Cartier” or “Tiffany & Co.” should show the maker’s signature and, often, a serial number, and ideally come with documentation. “In the style of” or “-style” means it is not by that maker. Treat a famous name in a description with care until the marks and paperwork support it.

8. Calculate the true cost before you bid

Add the buyer’s premium, applicable sales tax, shipping and insurance, and any sizing or repair. A ring that hammers at $1,000 can easily cost noticeably more by the time it fits your finger. Set your hard maximum with all of that included. My notes on the buyer’s premium and setting a hard max bid walk through the math.

9. Read the remedies before you need them

Before bidding, find the answers to three questions in the terms of sale:

• What does the house guarantee? (Authenticity of what, exactly, and for how long?)
• What happens if a stone is not what the description said?
• What payment methods are accepted? Some methods offer buyer protection and others do not.

If the terms are unclear, ask, and get the answer in writing.

A note on period and style

Descriptions such as “Art Deco,” “Victorian” or “Retro” describe a style, and sometimes a date range, but they are the cataloguer’s opinion. Construction details support a date: the cut of the stones (old mine and old European cuts are earlier than modern brilliants), the type of clasp and how the piece was made. If the era matters to you, ask what evidence supports it.

Dion Abadi is an Atlanta-based art and jewelry auctioneer, licensed in Georgia, Florida and South Carolina (license numbers and state lookups), and the author of The Collector’s Guide to Art, Jewelry, Watches & Auctions, which covers diamonds, colored gemstones, treatments and precious metals. Also see the longer guide to buying estate jewelry at auction. General information only; not an appraisal.