How Do Gold Buyers Test Gold? XRF, Acid Testing, Hallmarks and Karat Marks Explained

How Do Gold Buyers Test Gold? XRF, Acid Testing, Hallmarks and Karat Marks ExplainedIf you have ever wondered how a professional gold buyer knows whether a piece is really 10K, 14K, 18K or something else, the answer usually involves a combination of experience, markings and testing.

At Cash for Old Jewelry in Ambler, Pennsylvania, we evaluate gold jewelry and other precious-metal items for customers throughout Montgomery County, Bucks County, the Main Line and the greater Philadelphia area.
Understanding how gold is tested can help you feel more comfortable when bringing in jewelry for evaluation.
Gold Hallmarks and Karat MarksThe first thing a jewelry professional may look for is a hallmark.
Common gold markings include:
10K
14K
18K
22K
24K
You may also see numerical purity marks such as:
417
585
750
916
999
These numbers generally correspond to the percentage of pure gold in the alloy.
For example:
417 is approximately 41.7% gold, or 10K.
585 is approximately 58.5% gold, or 14K.
750 is 75% gold, or 18K.
916 is approximately 91.6% gold, or 22K.
However, a hallmark is only one piece of information.
A stamp does not automatically prove that a piece is genuine.
Jewelry can be incorrectly marked, altered, repaired or composed of multiple metals.
That is why professional buyers may use additional testing.
Visual ExaminationAn experienced jewelry professional can often learn a great deal before any testing begins.
They may look at:

• Construction
• Solder joints
• Wear patterns
• Color
• Clasps
• Hallmarks
• Manufacturer marks
• Areas where plating may be worn away

Sometimes an item that appears to be gold may actually be gold-filled, gold-plated or made from another metal.
Other times, a piece may be genuine gold but have parts made from lower-purity metal.
Acid TestingAcid testing is one of the traditional methods used to test gold.
A small sample of metal is usually rubbed onto a testing stone.
Different acids are then used to estimate the metal's purity.
For example, one acid may react differently with 10K gold than it does with 14K or 18K gold.
Acid testing has been used for generations because it is relatively simple and effective when performed properly.
However, like any testing method, it has limitations.
It tests the surface or sampled material and should be interpreted by someone who understands jewelry construction.
XRF TestingOne of the most useful modern methods for evaluating precious metals is X-ray fluorescence, commonly called XRF.
An XRF analyzer can examine the elemental composition of a piece without damaging it.
It can help identify metals such as:

• Gold
• Silver
• Platinum
• Palladium
• Copper
• Nickel
• Zinc

An XRF test can provide a detailed breakdown of the metals present in the area being tested.
This is extremely helpful when examining jewelry, coins, flatware and other precious-metal items.
Does XRF Tell You Everything?Not always.
XRF primarily analyzes the area near the surface of the item.
That means an experienced evaluator still needs to understand what is being tested.
For example, a heavily plated item could potentially show precious metal at the surface while having a different metal underneath.
A professional may use multiple methods when necessary.
Magnet TestingGold itself is not magnetic.
A strong magnetic reaction can therefore be a warning sign that an item contains a significant amount of ferrous metal.
However, magnet testing alone cannot prove whether something is gold.
Some non-gold metals are also