| Visual Inspection and Hallmark Check | Physical | Surface condition, stamps, plating wear, solder seams, magnet response, and obvious inconsistencies. | Inspect the item under bright, magnified light. Check the hallmark location, font consistency, edge wear, discoloration, and areas where plating may be thin. | Common fineness marks include 999, 916, 750, and 585 for gold, and 999, 950, 925, and 800 for silver. A hallmark alone is not proof of authenticity. | Fast, inexpensive, and non-destructive. | Counterfeit items can carry false marks. Some genuine items may have worn, incomplete, or region-specific markings. |
| Magnet Screening | Physical | Strong magnetic attraction caused by ferromagnetic base metals. | Move a strong magnet near the item without allowing it to scratch the surface. Observe attraction and movement. | Pure gold and pure silver are not ferromagnetic. Strong attraction suggests iron, nickel, cobalt, or another magnetic component. | Quick preliminary screening with no chemical exposure. | A non-magnetic response does not prove authenticity. Some counterfeit metals are also non-magnetic, and clasps or steel components may create localized attraction. |
| Acid Touchstone Test | Chemical | Resistance of the surface alloy to a calibrated acid solution. | Rub the item on a dark testing stone, apply an acid intended for a selected karat or fineness range, and compare the reaction with known reference needles or samples. | Gold testing solutions are commonly prepared for ranges such as 10K, 14K, 18K, and 22K. Higher-karat gold generally resists stronger acid better than lower-karat gold. | Low cost and useful for screening solid gold items. | It is a surface test and may miss thick plating or filled construction. Acids are corrosive; wear chemical-resistant gloves and eye protection, and use ventilation. |
| Silver Acid Test | Chemical | Reaction of the exposed metal with silver-testing acid, commonly based on nitric acid chemistry. | File or scratch a concealed area sufficiently to expose the underlying metal, then apply a small amount of test solution and compare the color and reaction. | High-silver alloys generally produce a characteristic light or creamy reaction, while copper-rich alloys may produce darker or greener reactions. Exact colors vary by solution and alloy composition. | Useful for distinguishing many silver alloys from copper or base-metal imitations. | Can permanently mark the item and may damage plating. Nitric-acid-based solutions require strict handling, ventilation, and appropriate protective equipment. |
| Specific Gravity Test | Physical | Density calculated from the item’s dry mass and its apparent mass when submerged in water. | Weigh the clean item in air, weigh it while fully suspended in water without touching the container, then calculate: SG = air weight ÷ (air weight − water weight). | Reference densities: pure gold ≈ 19.32 g/cm³; pure silver ≈ 10.49 g/cm³. Typical 18K gold is approximately 15–16 g/cm³, while sterling silver is approximately 10.2–10.4 g/cm³. | Non-destructive and more informative than a magnet test. | Results are affected by stones, hollow sections, trapped air, internal cavities, solder, and alloy composition. Use a precise scale and ensure complete immersion. |
| Electrical Conductivity Testing | Electronic | Electrical response related to alloy composition, conductivity, and geometry. | Place the clean item on the instrument’s sensor according to the device instructions and compare the reading with the expected range for the claimed metal and fineness. | Pure silver has very high electrical conductivity, approximately 62 MS/m at room temperature; pure gold is approximately 44 MS/m. Alloying substantially changes these values. | Fast and generally non-destructive; useful for screening coins, bars, and consistent items. | Readings vary with temperature, thickness, shape, surface condition, and hidden layers. A thin plated item may produce misleading results. |
| Ultrasonic Thickness Testing | Electronic | Internal continuity, thickness, and possible cavities or layered construction. | Apply suitable couplant and scan the item with an ultrasonic probe, comparing signal travel time and reflections across multiple points. | A solid item should show a consistent internal response. Strong reflections or unexpected thickness changes may indicate a hollow area, insert, or layered structure. | Can examine beneath the surface without cutting or drilling. | Requires trained operation, suitable geometry, and good probe contact. Very small, irregular, or highly ornamented pieces can be difficult to evaluate. |
| X-Ray Fluorescence (XRF) | Electronic | Elemental composition of the analyzed surface area. | Expose the clean item to X-rays and analyze the characteristic fluorescent radiation emitted by elements such as gold, silver, copper, zinc, and nickel. | Results are reported as element percentages or estimated fineness, such as Au 75.0% for approximately 18K gold or Ag 92.5% for sterling silver. | Rapid, non-destructive, and capable of identifying multiple alloying elements. | Usually analyzes only a shallow surface layer. Thick plating, surface segregation, dirt, curvature, and small measurement areas can affect results. Follow radiation-safety procedures. |
| Laser-Induced Breakdown Spectroscopy (LIBS) | Electronic | Elemental composition from a microscopic laser-generated plasma. | Focus a laser on a small area and interpret the emitted light to identify and quantify elements in the tested spot. | Can detect major elements and some trace elements, helping distinguish gold or silver alloys from plated or base-metal materials. | Provides localized compositional information and can investigate selected points. | Normally leaves a tiny ablation mark. Results depend on calibration, surface condition, and measurement location; professional operation is recommended. |
| Fire Assay | Chemical | Total precious-metal content after destructive separation and weighing or instrumental measurement. | A representative sample is fused with flux and collectors, separated from base metals, and analyzed using a cupellation or related laboratory procedure. | Considered a highly accurate method for determining gold content when sampling and laboratory controls are appropriate. Results may be expressed in parts per thousand, such as 999.9 fineness. | Suitable for definitive laboratory-grade analysis and bulk material verification. | Destructive, time-consuming, and dependent on a representative sample. It requires specialized equipment, trained personnel, and strict high-temperature safety controls. |