How to Test for Platinum? A Jeweler’s Guide

Testing for platinum isn’t a simple dip-and-see affair. It requires a multi-pronged approach, combining visual inspection, density testing, acid tests, and, in some cases, advanced analytical techniques. You need to consider the potential for deceptive markings and base metal alloys that mimic platinum‘s heft. The most reliable method involves a combination of methods that build upon each other, confirming the presence of platinum step-by-step.

The Comprehensive Platinum Testing Protocol

Here’s a breakdown of the techniques used by experienced jewelers and metal specialists:

1. Initial Visual Inspection: More Than Meets the Eye

Begin with a meticulous examination. Look for hallmarks. Platinum jewelry is usually stamped with markings like “PLAT,” “PT,” “950,” “900,” or “850,” indicating the platinum content (95%, 90%, or 85% pure, respectively). Be wary of stamps that seem inconsistent, poorly applied, or look altered.

• Hallmark Placement: Examine the location of the hallmark. In rings, it’s typically found inside the band. Pendants often have it near the bail or clasp.

• Magnification is Key: Use a jeweler’s loupe (10x magnification or higher) to inspect the hallmark and the piece’s overall surface. Look for pitting, porosity, or signs of wear and tear that might indicate a plated or filled piece.

• Color Assessment: Platinum typically has a grayish-white color. If the piece looks overly bright or yellowish, it could be white gold or another metal. However, platinum can be polished to a high shine, so don’t rely solely on color.

2. Density Testing: The Weight of Evidence

Platinum is significantly denser than other precious metals like gold or silver. This density provides a crucial clue.

• Archimedes’ Principle: The principle behind this test involves measuring the object’s weight in air and its weight when submerged in water. The difference allows you to calculate its volume, and from there, its density.

• Accurate Measurement: You need a highly accurate scale (sensitive to at least 0.01 grams) and a container of distilled water. Suspend the object from the scale using a thin wire or thread, ensuring it’s completely submerged without touching the sides or bottom of the container.

• Density Calculation: The density is calculated using the formula: Density = Weight in Air / (Weight in Air – Weight in Water). Platinum‘s density is approximately 21.45 g/cm³. Alloys, of course, will have slightly lower densities, but should still be significantly higher than gold (around 19.3 g/cm³) or silver (around 10.5 g/cm³).

• Consider Gemstones: If the piece contains gemstones, their volume needs to be accounted for to get an accurate density reading for the metal itself. This can be complex and may require estimating the gemstone’s volume or removing them if possible.

3. Acid Testing: The Platinum’s Resistance

Platinum is remarkably resistant to most acids. Acid testing involves applying specific acids to the metal and observing its reaction.

• Safety First: This test involves corrosive chemicals. Wear appropriate safety gear, including gloves, eye protection, and a lab coat. Work in a well-ventilated area.

• The Acid Kit: A standard acid testing kit includes solutions of nitric acid and aqua regia (a mixture of nitric acid and hydrochloric acid).

• Scratch Test: Scratch the piece lightly on a touchstone (a black testing stone). This creates a small sample of the metal to test.

• Nitric Acid Test: Apply a drop of nitric acid to the scratch. Platinum will not react. If the scratch dissolves or changes color, it’s not platinum.

• Aqua Regia Test: If the nitric acid test passes, apply a drop of aqua regia. Platinum will dissolve slowly in aqua regia, but other metals will dissolve much faster. Observe carefully.

• Neutralization and Disposal: After the test, neutralize the acid with baking soda and dispose of it properly according to local regulations.

4. Advanced Analytical Techniques: When Precision is Paramount

For definitive identification or precise determination of platinum content, more sophisticated techniques are used.

• X-ray Fluorescence (XRF): XRF is a non-destructive technique that bombards the sample with X-rays, causing the atoms to emit characteristic fluorescent X-rays. The wavelengths and intensities of these X-rays reveal the elemental composition of the sample. It’s fast, accurate, and doesn’t damage the piece.

• Inductively Coupled Plasma Mass Spectrometry (ICP-MS): ICP-MS is a highly sensitive technique that involves ionizing the sample in an argon plasma and then separating the ions by their mass-to-charge ratio. This provides extremely accurate quantification of even trace elements. It’s often used for geological samples and high-precision analyses of precious metals.

• Fire Assay: This is the traditional method for determining the precious metal content of ores and concentrates. It involves melting the sample with a flux, separating the precious metals, and then weighing them. While accurate, it’s a destructive technique and requires specialized equipment.

FAQs: Decoding the Mysteries of Platinum Identification

1. Can I test for platinum at home?

While visual inspection and basic density testing can be done at home, acid testing should be left to professionals due to the hazardous chemicals involved. For definitive identification, professional XRF testing is recommended.

2. What does “plat 950” mean?

“Plat 950” or “PT950” indicates that the piece is 95% pure platinum. The remaining 5% is typically other metals like iridium, ruthenium, or cobalt, added to improve hardness and durability.

3. How can I tell the difference between platinum and white gold?

Platinum is denser and heavier than white gold. Over time, white gold may require re-rhodium plating to maintain its bright white color, while platinum naturally develops a patina. Acid testing can also differentiate between the two.

4. Is there a magnet test for platinum?

Platinum is not magnetic. However, some platinum alloys may contain magnetic metals like cobalt. A weak magnetic attraction doesn’t necessarily rule out platinum, but it warrants further investigation.

5. What is the difference between platinum and palladium?

Both are precious metals in the platinum group, but platinum is denser and more expensive than palladium. They also have different reactions to acids.

6. Why is platinum so expensive?

Platinum is rarer than gold, harder to mine, and has a higher melting point, making it more challenging to work with. Its industrial uses also contribute to its demand and price.

7. Can platinum be fake?

Yes, platinum can be faked using base metals like steel or tungsten coated with a thin layer of platinum or white gold. This is why thorough testing is crucial.

8. How does age affect platinum testing?

Older platinum pieces may have accumulated dirt and oxidation, affecting visual inspection and density readings. Cleaning the piece carefully before testing is essential.

9. What is the best acid to test for platinum?

Aqua regia (a mixture of nitric acid and hydrochloric acid) is the best acid to test for platinum, as it will slowly dissolve platinum while leaving other metals unaffected.

10. Can XRF testing damage jewelry?

No, XRF testing is a non-destructive technique. It does not damage the jewelry in any way.

11. What is the significance of the “iridplat” hallmark?

“Iridplat” indicates an alloy of iridium and platinum. The exact proportions will vary, but it signifies the presence of iridium in the platinum alloy.

12. How reliable are electronic platinum testers?

While some electronic testers claim to identify platinum, they are generally less reliable than density testing and acid testing. They should only be used as a preliminary screening tool and not as definitive proof of platinum. Always double-check the results with other methods.