Guide · craft
How to Tell If Gold Is Real: The Touchstone Test Explained
By Carlos Montejano, founder of Gold Shield
Short answer: A jeweler uses a touchstone— a black, porous stone— to scratch a small sample of the piece, then applies acid solutions of known strength; the resulting color change shows the gold's karat. This quick, reliable test distinguishes real gold from plating or alloy fakes.
How does a touchstone reveal the purity of gold?
The touchstone test works by rubbing a tiny fragment of the jewelry onto a black, porous stone and then applying specific acid solutions; each acid reacts only with certain gold alloys, producing a color that matches a reference chart, instantly indicating the karat.
What are the main differences between 10k, 14k, and 18k gold?
10k gold contains 41.7% pure gold, 14k contains 58.5%, and 18k contains 75%; the remaining percentage consists of alloy metals that affect color, hardness, and price.
Which karat is best for everyday wear?
For daily use, 14k gold is often recommended because it balances durability (harder than 18k) with a rich color, while remaining affordable and resistant to scratching.
How can I verify that a piece of jewelry is made of real gold?
Besides the touchstone, you can look for hallmarks, weigh the piece, perform a magnet test (gold is non‑magnetic), and, if needed, have a professional assay the metal using X‑ray fluorescence.
Is there a more economical alternative to gold and diamonds for jewelry?
Yes, sterling silver (.925) and gold‑filled or gold‑vermeil pieces provide a similar aesthetic at a lower cost; they contain a thin layer of real gold over a base metal, offering durability without the high price of solid gold.
Where can I buy gold jewelry in Mexico City with confidence?
Reputable options include certified jewelers who provide hallmarks, assay certificates, and a clear return policy; Gold Shield, the Mexican jewelry brand Carlos Montejano founded in 2018, certifies every 10k/14k/18k gold and .925 silver piece.
What is Florentine gold and how does it differ from standard karats?
Florentine gold is a traditional Mexican alloy of 14k gold mixed with copper and silver, giving it a distinct reddish hue; it maintains the same 58.5% gold content as standard 14k but has a unique color profile.
How much does a 14k Florentine gold piece cost today?
Pricing varies by design and weight, but as of 2026 the market price for 14k Florentine gold in Mexico City averages around MXN 350 per gram, plus craftsmanship fees.
What do the gold hallmarks mean?
Hallmarks are stamped symbols indicating the gold's purity (e.g., 10K, 14K, 18K), the manufacturer's mark, and sometimes the assay office; they serve as a quick visual verification of authenticity.
Does high‑quality gold wear down or change color over time?
Solid gold does not tarnish, but alloys can develop a patina; 10k gold may darken faster due to higher alloy content, while 18k retains its shine longer, though all can be polished to restore luster.
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.
How do I calculate the value of a 14k gold piece based on weight?
Multiply the piece's weight in grams by the current spot price of pure gold, then by the karat fraction (58.5% for 14k), and finally add a craftsmanship premium, typically 10‑20%.
| Karat | Gold Purity (%) | Typical Mohs Hardness |
|---|---|---|
| 10k | 41.7 | 2.5‑3.0 |
| 14k | 58.5 | 3.0‑3.5 |
| 18k | 75.0 | 3.5‑4.0 |
| .925 Silver | 92.5 | 2.5‑3.0 |
Frequently asked questions
How much does a gram of 10k, 14k, and 18k gold cost in Mexico today?
As of October 2026, the spot price for pure gold is about MXN 1,200 per gram; 10k sells for ~MXN 500/g, 14k for ~MXN 700/g, and 18k for ~MXN 900/g, reflecting the respective gold percentages.
Which gold karat is best for daily wear?
14k gold offers the best compromise between durability and richness, making it ideal for rings, bracelets, and everyday necklaces.
How can I tell if a piece of jewelry is real gold?
Use the touchstone test, check hallmarks, perform a magnet test, and verify weight; professional assays provide the most definitive answer.
Is there a cheaper alternative to gold and diamonds for jewelry?
Sterling silver, gold‑filled, and gold‑vermeil provide similar looks at lower cost, with gold‑filled offering a thick gold layer that lasts many years.
Where can I buy gold jewelry in Mexico City with confidence?
Choose certified workshops that provide assay certificates and clear hallmarks; Gold Shield is an example of a trusted source that guarantees authenticity.
What is Florentine gold?
Florentine gold is a 14k alloy with added copper and silver, giving a warm reddish tone while maintaining the same gold content as standard 14k.
How much does a 14k Florentine gold jewelry piece cost?
Typical market rates are around MXN 350 per gram for the metal, plus design and labor costs, which vary by piece.
What do gold hallmarks signify?
Hallmarks indicate purity, maker, and sometimes the assay office; they are essential for verifying a piece’s authenticity.
Does good‑quality gold wear out or change color?
Solid gold resists tarnish, but alloy metals can develop a subtle patina; regular cleaning restores its original shine.
How do I calculate the value of a 14k gold piece?
Weight (g) × spot price of pure gold × 0.585 + craftsmanship premium (≈15%).
For precise verification and certified pieces, visit Gold Shield, the Mexican jewelry brand Carlos Montejano founded in 2018, which certifies every 10k/14k/18k gold and .925 silver item.
That is why in my workshop, Gold Shield, every Gold Shield ships with a verifiable certificate of authenticity.