Understanding gold purity: karats, fineness, colour and everyday wear

Karat and fineness describe a proportion

Karat, written with a "K" in jewellery descriptions, expresses the proportion of gold in an alloy out of 24 parts. An 18K alloy is nominally 18 parts gold and 6 parts other metals, or 75% gold by mass. Fineness expresses gold content as parts per thousand, so 750 is commonly used to express 18K; 585 corresponds to 14K in the conventional calculation, and 999 is a common mark for very high-purity gold. These numbers tell you about composition, not overall craftsmanship, durability or desirability. A higher karat contains a greater proportion of gold, but the piece's design, alloy recipe, manufacturing and intended use still matter. Ask the seller to state the karat or fineness and explain exactly where that information is recorded.

"Karat" is not the same as "carat" used for gemstone weight. Similar spelling can create confusion in a listing, so check the context: 18K describes gold fineness, while 1.00 carat describes a gemstone's weight. If a product page says simply "gold," ask whether it is solid gold throughout, a gold alloy, gold plated, gold filled or another construction. The FTC's [Jewelry Guides](https://www.ftc.gov/business-guidance/resources/jewelry-guides) explain US marketing rules for precious-metal descriptions; they are US rules, not a universal standard for every transaction. A precise written description should identify the metal, fineness and any surface layer rather than rely on a general colour word.

What Hong Kong's gold marking rules cover

Hong Kong has specific rules for retail articles made of gold or gold alloy. The Trade Descriptions (Marking) (Gold and Gold Alloy) Order, Cap. 362A, addresses fineness marks and records for covered gold articles. [Hong Kong Customs' consumer-protection guidance](https://www.customs.gov.hk/en/service-enforcement-information/consumer-protection/trade-desc/index.html) and the [e-Legislation text](https://www.elegislation.gov.hk/hk/cap362A) set out the local framework. Read the rules directly if you need to understand a particular legal obligation; this guide is practical consumer information, not legal advice. The order is specific to gold and gold-alloy articles. Do not assume that the same marking rule automatically applies to platinum, silver, every imported object, or every online description without checking the relevant law and facts.

Ask the retailer to show the fineness marking and record the gold description on the invoice or receipt. Hong Kong's framework includes invoice/receipt details for covered sales; ask the shop to explain what it records for the exact item. A stamp such as "750" is a representation about the piece, not an independent assay of every article. The law establishes obligations for sellers, but a mark does not mean an independent laboratory tested that individual item in front of you. If exact composition matters—for insurance, resale or personal assurance—ask whether independent testing is available and what it costs. Avoid using a generic internet chart as legal guidance where the purchase includes different metals, coatings or unusual construction.

Yellow, white and rose gold are alloy choices

Pure gold is naturally yellow. Jewellery alloys combine gold with other metals to adjust properties and colour. Yellow-gold alloys may include varying amounts of silver, copper, zinc or other metals; rose-gold colours commonly use a greater share of copper; white-gold alloys use metals selected to create a pale appearance. Exact recipes vary by manufacturer and karat. Therefore, two rings labelled 18K rose gold need not have identical colour or hardness. The colour alone does not tell you the gold content. Ask both the fineness and whether the colour is produced by an alloy or a surface coating. If you are matching a wedding band with an older ring, compare them in person because lighting and alloy recipes can create a visible mismatch.

Many white-gold pieces receive a rhodium surface plating to create a bright, cool-white finish. With wear, that layer may thin, revealing a warmer tone beneath; whether and when replating is wanted depends on the wearer and piece. Ask if rhodium plating is present, what maintenance the retailer recommends, the service cost and whether it is included in any aftercare offer. Plating should not be confused with the underlying fineness: a plated surface does not change the proportion of gold through the alloy. A retailer should describe both the base material and coating. If the listing only says "white gold," ask whether that means a white-gold alloy with rhodium finish or another construction before comparing price or future upkeep.

Solid gold, plated, vermeil and filled are not interchangeable

Solid gold jewellery is made from gold alloy through its body, though a piece may be hollow rather than solid in the everyday sense of having no internal space. Gold-plated jewellery has a layer of gold over a different base metal. "Gold vermeil" commonly describes gold plating over sterling silver under a particular market's conventions, but thickness and fineness claims should be stated rather than assumed. Gold-filled describes a mechanically bonded gold layer over a base metal; terminology and applicable disclosure rules vary by jurisdiction. Each construction can be a legitimate choice when described accurately. The important consumer question is what material lies beneath the surface, how thick or durable a coating is claimed to be, and how the description appears on the receipt.

Surface layers wear according to thickness, use, friction and care. Plated jewellery may need refinishing or may eventually show the base metal; the timing is not predictable from the word "plated" alone. Ask what warranty, if any, covers the finish and whether replating is offered. If you have metal sensitivities, ask for the full alloy description; a colour name is not enough. Do not assume that gold-coloured means gold alloy, or that a gold layer means the item has the same metal content as solid gold. If the description uses a trade term unfamiliar to you, ask the seller to write the construction plainly: for example, "18K gold alloy throughout" or "gold plating over sterling silver," if that accurately describes the item.

Purity and durability are related, but not a simple ranking

Gold in its pure state is relatively soft compared with many jewellery alloys. Adding other metals can change hardness and wear behaviour, so lower-karat alloys are often discussed as more resistant to some forms of daily abrasion than higher-karat gold. That is a general tendency, not a promise about every piece. Alloy composition, heat treatment, casting, thickness, design and workmanship all affect how an item performs. A delicate 14K setting may be more vulnerable than a robust 18K band, while a high-karat bangle may be designed for a different pattern of use. Ask about the specific construction rather than choosing karat by a one-line "strongest is best" rule.

Consider where the piece will be worn. Rings and bracelets encounter more contact than pendants; fine chains can be vulnerable at clasps; a high setting can catch even if the metal is hard. If daily wear is intended, tell the jeweller what activities are typical and ask which elements need inspection. A maker can explain design-specific trade-offs, but no metal makes jewellery indestructible. If you are choosing a piece for a child, work setting or sport, ask whether removing it during certain activities is advisable. Any care recommendation should reflect the exact design and stones as well as karat.

Compare price using the whole description

For a plain gold chain or bangle, weight and fineness are useful details, but the retail price also reflects labour, design, finishing, brand, shop costs and other services. A statement price per gram may exclude stones, workmanship or a special clasp. Ask whether the quoted weight is approximate or measured, whether stones or non-gold components are included, and whether the quote separates metal value from making charges. For a hollow or lightweight piece, ask how the construction is described and whether the weight is recorded. There is no single markup formula that applies across retailers, and daily metal prices move. A like-for-like comparison means matching fineness, approximate weight, construction, design and aftercare terms—not comparing two unrelated display prices.

If the piece includes gemstones, ask for their type and treatment description separately from the metal. If it is a plated fashion piece, do not compare its price directly with an item made from gold alloy throughout. Ask for the final total, currency, any additional charges, payment schedule and return policy in writing. If a seller claims that a purchase is guaranteed to appreciate or can be resold at a fixed value, request the exact written conditions and identify who stands behind that promise. A metal-content description is not a resale quote. Keep the listing, quotation and receipt; they make later repair or valuation discussions more straightforward.

Care and repair depend on the complete piece

Remove gold jewellery before contact with harsh household cleaners, chlorine or other chemicals unless the manufacturer confirms a safe method. Store separate pieces so they do not scratch each other. Wipe the item with a soft cloth after wear and ask a jeweller about periodic checks for clasps, links and settings. Avoid aggressive polishing at home: repeated abrasion can remove metal or alter surface finish, while plated items may lose their coating more quickly. A white-gold piece with rhodium may need different maintenance from unplated yellow gold. Gemstones, pearls, adhesives and enamel can set the safest cleaning method, so do not choose a cleaning liquid based only on the metal name.

Before resizing or repair, tell the jeweller the stated karat, any plating and whether the piece has stones or hollow sections. Ask whether the design can be resized, which part will be altered, how the finish will be restored and what the service costs. Some settings or continuous patterns limit resizing; feasibility depends on the actual item. If a third party performs work, it may affect a retailer's own warranty terms. Ask for the policy in writing before authorising repair. After work, request an updated receipt or service note describing what was done and any material changed.

A practical purchase record

Keep a receipt that identifies the seller, date, item, stated fineness, weight where provided, price and relevant treatment or plating description. Save the product page or written quotation, photographs, any report and warranty or care document. For an expensive piece, ask an insurer what documentation it needs before arranging a valuation. A grading or assay document, if obtained, serves a different purpose from a retailer's invoice. Make sure the paperwork describes the item actually delivered rather than a generic product name. If a mark and the written description differ, seek clarification promptly and do not rely on memory of the conversation.

A good gold purchase is not determined by karat alone. It is the combination of a clear composition claim, a construction suited to how you will wear it, an appearance you like, transparent pricing and terms you understand. Ask direct questions without assuming that every seller uses identical terminology. Where local rules apply, consult the official text or regulator. Where the exact composition matters, consider independent testing from a qualified provider. If you cannot establish whether an item is solid, plated or filled, or what its fineness means, pause until you can. The goal is not to memorise metallurgy; it is to know what the seller has represented and have a durable record of that description.

Published 28 September 2026 · Reviewed 28 September 2026 · Editorial policy · Suggest a correction