Recognizing real gold: simple tests

At a glanceIn an era of sophisticated counterfeits, knowing how to reliably identify real gold is an essential safeguard for investors and collectors in Switzerland. While simple bench tests quickly weed out crude imitations, advanced deceptive techniques (such as tungsten-cored gold bars) require rigorous non-destructive physical testing. This guide presents comprehensive testing protocols.

1. Visual Inspection and Official Swiss Hallmarks

Begin with a 10x jeweler's loupe (triplet aplanat):

• Official fineness stamp: Under the Swiss Precious Metals Control Act (LCMP), genuine gold items must bear fineness marks in thousandths (750 for 18k, 585 for 14k, 375 for 9k).
• Official state guarantee mark: The Saint-Bernard Dog's Head is the official Swiss hallmark applied by federal assay offices to certify precious metals.
• Maker's responsibility mark: Registered with the Central Office in Bern, identifying the licensed manufacturer or importer.
• Edge wear examination: Inspect high-friction points like clasps and link joints. If a reddish or grayish base metal appears underneath, the item is gold-plated.

2. The Magnet Test (Diamagnetism)

Gold is strictly diamagnetic—it is slightly repelled by magnetic fields and never attracted:

• Use a rare-earth neodymium magnet (rated N52).
• If the object sticks or jumps to the magnet, it contains iron, nickel, or cobalt: it is an absolute counterfeit.
• *Test limitation:* Copper, brass, and lead are also non-magnetic. Passing the magnet test does not prove authenticity on its own.

3. Archimedes' Hydrostatic Specific Gravity Test

The most elegant and reliable bench method for solid jewelry and coins:

Equipment Needed:

• Precision digital balance with 0.01 g readability.
• Beaker of distilled water and thin sewing thread.

Protocol:

1. Weigh dry item on the scale: record dry mass in air ($M_1$).

2. Place beaker of water on the balance and tare to 0.00 g.

3. Suspend item by thread fully submerged in water without touching the bottom or sides. The reading equals the item's volume in $cm^3$ ($V$).

4. Calculate density: $ρ = M_1 ÷ V$.

Density Benchmark Chart

The Tungsten Bar Threat and How to Defeat It

Because tungsten has nearly the exact same density as fine gold (19.25 vs. 19.32 g/cm³), hydrostatic weighing cannot detect a tungsten slug clad in gold.

The solution: Ultrasonic sound velocity testing. In Swiss bullion houses, acoustic testers measure sound propagation speed. Sound travels through pure gold at 3,240 m/s, but reaches 5,220 m/s in tungsten. The ultrasound device detects composite cores in 2 seconds through intact blister packaging.

Frequently Asked Questions (FAQ): Spotting Real Gold

Is the bite test reliable?

No! While pure 24k gold is soft, lead is even softer. Biting coins dents collector coins and destroys their numismatic premium.

Does real gold leave streaks on unglazed ceramic?

Yes, gold leaves a golden streak on unglazed ceramic, whereas fool's gold (pyrite) leaves black streaks. However, this test irreversibly scratches your jewelry.