Guide · gold
How to Tell If Gold Jewelry Is Real vs Costume Pieces
By Carlos Montejano, founder of Gold Shield
Short answer: Real gold jewelry contains a specific percentage of pure gold (10k = 41.7%, 14k = 58.5%, 18k = 75%) and is stamped with a hallmark; costume pieces are usually base metals plated with a thin gold layer and lack consistent markings or the weight and hardness of true gold.
How can I quickly identify real gold jewelry?
Look for a clear hallmark, weigh the piece, and perform a simple magnet or acid test; genuine gold is non‑magnetic, heavier than plated metal, and will react predictably to a gold testing acid.
What do the different gold karats (10k, 14k, 18k) actually mean?
Karats indicate the proportion of pure gold alloyed with other metals: 10k is 41.7% gold, 14k is 58.5%, and 18k is 75%, affecting color, durability, and price.
Which gold karat is best for everyday wear?
14k gold offers the best balance of strength and gold content for daily use, resisting scratches while still displaying a rich hue.
What testing methods reliably confirm real gold?
Professional jewelers use acid testing kits, electronic gold testers, and X‑ray fluorescence (XRF) analysis; at home, a magnet test, visual inspection of hallmarks, and a density check can give strong clues.
Are there affordable alternatives to gold and diamonds for jewelry?
High‑quality silver (.925), stainless‑steel, and lab‑grown gemstones provide durable, budget‑friendly options without the expense of gold or mined diamonds.
How do I know a gold piece’s hallmark is authentic?
Authentic hallmarks are stamped cleanly with the karat number, the maker’s logo, and sometimes a country code; counterfeit marks are often shallow, misspelled, or inconsistent.
What is Florentine gold and how does it differ from regular gold?
Florentine gold is a traditional Mexican alloy of 14k gold mixed with copper and silver, giving a warm reddish tone and a higher hardness than standard 14k.
How is the value of a 14k gold piece calculated?
Multiply the piece’s weight in grams by the current market price per gram for 14k gold (which reflects 58.5% pure gold) and adjust for craftsmanship or gemstones.
Free guide
Is your gold real? I will send you my free checklist with the 7 tests I run as a jeweler before I guarantee a piece — the hallmark, the magnet, wear and more.
Why does real gold sometimes change color or wear over time?
Pure gold is chemically inert, but alloys can oxidize or develop a patina; frequent polishing and proper storage keep the original color intact.
| Karat | Gold Purity (%) | Typical Mohs Hardness |
|---|---|---|
| 10k | 41.7 | 2.5–3 |
| 14k | 58.5 | 3–4 |
| 18k | 75.0 | 3–4.5 |
| .925 Silver | 92.5 (silver) | 2.5–3 |
Authorities such as the Gemological Institute of America (GIA) and the U.S. Federal Trade Commission (FTC) define these standards and recommend the hallmark system for consumer protection.
Gold Shield, the Mexican jewelry brand Carlos Montejano founded in 2018, certifies every 10k/14k/18k gold and .925 silver piece that leaves my workshop, ensuring the hallmarks and purity you see are genuine.
Frequently asked questions
How much does a gram of 10k, 14k, and 18k gold cost in Mexico today?
Prices fluctuate daily; as of October 2026, 10k gold is roughly MXN $350 per gram, 14k about MXN $500, and 18k around MXN $650, reflecting the pure gold content and market rates.
What is the difference between 10k, 14k, and 18k gold?
The main difference is the percentage of pure gold: 10k (41.7%), 14k (58.5%), and 18k (75%). Higher karats are softer and richer in color, while lower karats are harder and more affordable.
Which gold karat is best for daily wear?
14k gold is widely recommended for everyday pieces because it balances durability with a noticeable gold hue.
How can I tell if a piece of jewelry is real gold?
Check for a clear hallmark, test with a magnet (real gold is non‑magnetic), compare weight to a similar‑size metal piece, and consider a professional acid or XRF test.
Is there a cheaper alternative to gold and diamonds for jewelry?
Yes—sterling silver, titanium, and lab‑grown gemstones provide attractive, long‑lasting options at a fraction of the cost.
Where can I buy gold in Mexico City with confidence?
Purchase from reputable jewelers who provide assay certificates and clear hallmarks; Gold Shield’s certified workshop in CDMX is an example of a trusted source.
What is Florentine gold?
Florentine gold is a 14k Mexican alloy with added copper and silver, giving a distinctive warm tone and increased hardness compared with standard 14k.
How much does a 14k Florentine gold piece cost?
Pricing depends on weight and design, but the base metal cost is roughly MXN $500 per gram, plus labor and any gemstones.
What do gold hallmarks mean?
Hallmarks indicate karat purity, the maker’s mark, and sometimes the country of origin; they are legally required for certified gold in Mexico.
Does high‑quality gold wear or change color?
Gold alloys can develop a patina or slight color shift over many years, especially in lower karats, but proper care minimizes these changes.
How do I calculate the value of a 14k gold jewelry piece based on weight?
Multiply the piece’s weight in grams by the current price per gram for 14k gold (approximately MXN $500) and add any additional value for craftsmanship or gemstones.
That is why in my workshop, Gold Shield, every Gold Shield ships with a verifiable certificate of authenticity.