Ownership, care & collecting

The first check is the seller. Established jewelers and dealers supply references, belong to trade organizations with codes of conduct, and describe the stone fully, treatment included, on the invoice. GIA's buying guide advises working with trained staff, such as holders of its Graduate Gemologist or Applied Jewelry Professional credentials, and asking for a grading report.

A laboratory report, often called a certificate, describes a stone as examined; it is not a valuation. For a diamond, check that the report number matches any girdle inscription and confirm it online through GIA's Report Check service. For a colored stone, the report should state whether treatment was detected and, where it matters to price, give a recognized laboratory's opinion of geographic origin. Laboratories differ in strictness, so price comparisons are most meaningful between stones graded by the same lab.

The Federal Trade Commission's Guides for the Jewelry, Precious Metals, and Pewter Industries (16 CFR Part 23) are administrative guides rather than a freestanding prohibition, and they apply in the United States only. They set out when the FTC will treat a failure to disclose a gemstone treatment as deceptive: where the treatment is not permanent, creates special care requirements, or significantly affects the stone's value. For online purchases, GIA recommends stones with reports from reputable laboratories, 360° views and a confirmed return policy. A written return period also lets the buyer have the stone checked by an independent gemologist or appraiser.

How a stone survives daily wear depends on three separate properties. Hardness resists scratching, toughness resists chipping and breaking, and stability resists heat, light and chemicals. Topaz rates 8 on the Mohs scale but has a cleavage, a plane along which it can split, so a sharp knock may break it. Jade rates only about 6–7 yet is exceptionally tough. Pearl and amber are soft, and pearls are damaged by acids in perfume, cosmetics and perspiration.

Ultrasonic cleaners loosen dirt with high-frequency vibration, and steam cleaners blast it away with hot pressurized steam. Both can widen fractures, split stones along cleavage, drive out the oils or resins used as fillers and shock heat-sensitive gems. GIA's gem-by-gem guidance, summarized in the table, treats warm soapy water and a soft brush as the safe method for nearly all gems. It calls both machines safe for untreated or heat-treated ruby and sapphire and advises against them for emerald, opal, pearl, tanzanite, turquoise and moonstone. The safe, caution and avoid ratings in that table are this encyclopedia's own three-way scheme, mapped from GIA's wording rather than published by GIA. For diamonds, GIA advises against both at home because vibration can loosen stones in their settings.

Store jewels separately in soft pouches or divided boxes: diamond and corundum scratch softer gems and metals. Remove rings for heavy manual work and have prongs checked, since a worn setting can release a stone.

Standard homeowners and renters policies in the United States usually cap jewelry theft cover at a low amount: Jewelers Mutual, a US jewelry insurer, says homeowners insurance usually covers only US$1,000 to US$2,500 for jewelry. That is one insurer's figure, not an industry standard, and it does not describe cover outside the United States. Owners of valuable pieces therefore buy a separate jewelry policy or list items on an endorsement, which can extend cover to loss and damage as well as theft.

The insured amount usually comes from an insurance appraisal, which estimates retail replacement value: what a comparable new piece would cost. An appraisal states a value of a defined type for a stated intended use, replacement cost for insurance, fair market value for tax, and is not a statement of what a stone would fetch on resale, which is normally far lower. A useful appraisal names the appraiser and their qualifications, describes each stone and metal with measurements, weights, grades and treatments, and includes photographs. Jewelers Mutual sets no re-appraisal interval; it adjusts the insured amount automatically every two years at renewal. Insurers generally need an appraisal or equivalent proof of value at claim time, even if none was required when the policy began.

Keep a file for each piece: invoice, laboratory reports, appraisals, photographs and repair receipts. Store copies away from the jewelry, so they survive the same fire or burglary.

Selling a gem is slower than buying one, and sellers rarely recover the purchase price: retail prices carry several margins.

A buyback or trade-in is offered by some retailers for pieces they sold, and both Signet chains limit it to diamonds. Kay states that colored gemstones are not eligible, and Zales excludes gemstones and pearls. The terms differ too: Kay pegs the new piece to twice the trade-in value, Zales to twice the original purchase price. The owner gets store credit, in store, no cash.

Selling outright to a dealer is quicker, and the offer builds in the buyer's margin: in the Bain and AWDC value chain for 2012, polished diamonds changed hands at 31.3% of the consumer price. On consignment, a dealer displays the piece and pays only if it sells; the owner keeps title, so the agreement should set minimum price, commission, duration and insurance.

Auction suits important, documented stones. The house sets an estimate and often a reserve, charges an unpublished seller's commission, and adds a buyer's premium: from 1 September 2026, 28% on the first US$2 million at Christie's and Sotheby's, or the first £1,500,000 in London. Christie's charged 27% to US$1.5 million before that date.

A pawn is a loan against the item, not a sale. The UK regulator found in 2018 that British pawnbrokers lend about 50% of their own valuation; the item is sold only if the loan goes unredeemed.

Gems are easy to overlook in an estate and to argue over. An inventory with photographs, reports and appraisals tells executors what exists and where, and specific bequests reduce disputes over lookalike jewels. Heirs must know where documents and keys are.

Tax valuations use a different standard. In the United States, IRS Publication 561 defines fair market value as the price property would change hands at between a willing buyer and seller, neither forced to act, both knowing the relevant facts. Sentimental value does not count, and donations above US$5,000 need a qualified appraisal. It also wants gems and jewelry appraised by a specialist weighing cut, color, carat weight, flaws and fashion, and notes a famous former owner may add value. US federal law treats gems as collectibles: 26 USC 408(m)(2) names “any metal or gem”, and 26 USC 1(h)(5) defines collectibles gain by reference to it, giving a maximum 28% federal rate on gems held over a year.

Other countries differ. In the United Kingdom only, as of 2026, inheritance tax is 40% above the £325,000 nil-rate band, and gifts within seven years of death can still be taxed. That is no cliff edge: where gifts in those years exceed £325,000, taper relief cuts the rate on the excess to 32% at three to four years, 24% at four to five, 16% at five to six, 8% at six to seven, nothing after seven.

Collectors pursue gems for rarity, beauty or completeness rather than for wear. Some try to assemble every gem species, including collector stones such as benitoite, painite, grandidierite and taaffeite, which usually come in small sizes and often need laboratory testing to identify with confidence. Others collect one species in every color, or stones from classic localities. Because rare species trade infrequently, prices are hard to confirm and resale can take time.

Pairs and suites add the problem of matching. A pair for earrings must agree in color, tone, size, cut and clarity, and a suite of several stones for a necklace or a parure (a matched set of jewels such as necklace, earrings and bracelet) multiplies that difficulty. Well-matched groups are hard to assemble and are usually priced accordingly.

Mineral specimens and cut stones form overlapping but distinct markets. A specimen is valued as an intact natural crystal, often still attached to its host rock (the matrix), for its shape, luster, color, locality and overall look. Cutting a fine specimen destroys that value even if the gem inside is clean.

Finally, a provenance file, the documented chain of ownership, protects both value and title. It should hold invoices, laboratory reports, earlier auction catalogs, photographs, import and export papers and correspondence. For historic or royal pieces, documented ownership can raise auction prices well above those of comparable stones without it.