--- title: "How Is Gold Tested by Dealers?" source: "https://goldealers.co.uk/knowledge/testing/how-is-gold-tested-by-dealers" date: "2025-12-02" --- # How Is Gold Tested by Dealers? Buyers like Goldealers need to verify gold's authenticity and purity. This article explains the common testing methods dealers use to ensure they know what carat gold they're buying. At Goldealers, we primarily use non-destructive XRF analysis, but we cover all methods: electronic testing, acid tests, and more. > **Quick Summary:** Dealers use a combination of methods to test gold. First, they check for official hallmarks. Then they often use devices like XRF analysers that can scan the metal and instantly report its composition. Traditional acid tests are also used – a small rubbing of the gold is exposed to nitric acid to confirm its carat. Other tools include electronic testers and simple magnet checks (real gold isn't magnetic). Goldealers primarily uses non-destructive testing (like XRF), ensuring accurate results without damaging your item. ## Visual Inspection & Hallmarks The first step in testing any gold item. ### Initial Assessment **What Dealers Look For:** **Visual Clues:** - Colour (yellow, white, rose indicates gold type) - Weight (gold is very dense) - Wear patterns (plating shows through at edges) - Construction quality - Obvious damage or repairs - Surface condition **Hallmark Inspection:** - UK hallmarks (lion, number, assay office mark) - Foreign marks (14K, 750, etc.) - Maker's marks - Date letters (on antiques) - Consistent with item age and origin **Quick Indicators:** - "GP" or "GF" = plated/filled (not solid) - "925" = sterling silver (not gold) - No mark on heavy item = suspicious - Worn areas showing different colour = plated **Limitations:** - Hallmarks can be fake - Marks can wear off - Foreign pieces may have unfamiliar marks - Visual alone isn't definitive - Verification testing needed > Experienced dealers can make educated guesses from visual inspection, but always verify with technical testing. Never trust appearance alone for valuable items. [Complete guide to UK hallmarks](/knowledge/gold/understanding-gold-hallmarks-uk) ## X-Ray Fluorescence (XRF) The modern gold standard for testing precious metals. ### How XRF Works **Technology Overview:** **Basic Principle:** - Device emits X-rays at sample - Atoms in metal absorb energy - Atoms emit secondary X-rays (fluorescence) - Each element has unique fluorescence pattern - Detector identifies elements present - Computer calculates percentages **Process:** - Place item on XRF window or point handheld gun - Press trigger/start button - X-rays fired at metal (seconds only) - Results display on screen - Shows all elements detected - Percentages calculated **What XRF Reveals:** - Gold percentage (e.g., 75% = 18ct) - Silver content - Copper content - Other alloy metals - Any unexpected elements - Precise composition **Example Reading:** ``` Gold (Au): 75.2% Silver (Ag): 15.1% Copper (Cu): 9.7% = 18ct yellow gold ``` ### Advantages of XRF **Why Goldealers Uses XRF:** **Non-Destructive:** - No scratch required - No acid applied - Item remains pristine - Perfect for valuable pieces - Customers appreciate care **Speed:** - Results in 5-30 seconds - Multiple items tested quickly - Efficient for busy operations - Immediate confirmation - No waiting for reactions **Accuracy:** - Precise to 0.1% typically - Identifies exact composition - Detects unexpected elements - Reliable and consistent - Laboratory-grade results **Versatility:** - Works on any gold purity - Tests silver, platinum, palladium too - Handles unusual alloys - Various shapes and sizes - Coins, jewellery, bars all testable **Documentation:** - Printable results - Digital records - Clear evidence - Quality assurance - Customer transparency > XRF machines cost £10,000-£50,000+ depending on model. Goldealers' investment in professional equipment ensures accurate, non-destructive testing for all customers. ### Limitations of XRF **What to Know:** **Surface Reading:** - Analyses surface layers (0.1-0.5mm deep) - Heavy gold plating can fool basic XRF - Quality XRF reads deeper - Can test filed area if suspicion **Sample Size:** - Very small items (tiny flakes) difficult - Need sufficient surface area - Minimum size requirements - Larger items easier **Mixed Construction:** - Hollow items may show only outer layer - Solder joints different composition - Test multiple points for accuracy - Goldealers tests several areas **Calibration:** - Requires regular calibration - Against known standards - Professional maintenance needed - Goldealers maintains equipment rigorously [Detailed XRF explanation](/knowledge/testing/what-is-xrf-testing) ## Acid Testing Traditional but effective method still used today. ### Acid Test Process **How It Works:** **Materials Needed:** - Test stone (black touchstone) - Gold testing acids (various strengths) - Item to test - Scratch tool (if needed) **Testing Procedure:** **Step 1: Make Test Mark** - Rub item on stone (inconspicuous area if possible) - Leaves gold streak on stone - Small amount of metal transferred - Stone has fine texture that holds metal **Step 2: Apply Acid** - Different acid bottles for different karats - 9ct, 14ct, 18ct, 22ct acids available - Drop acid on streak - Observe reaction **Step 3: Interpret Results** - Gold dissolves in acids lower than its purity - Remains if gold is higher purity than acid - Example: 18ct gold won't dissolve in 18ct acid, but will in 14ct acid - Colour changes indicate purity range **Chemical Reactions:** - Nitric acid (various strengths) - Lower karat golds more reactive - Higher karat more resistant - Pure 24ct gold very acid-resistant - Base metals dissolve quickly ### Acid Test Accuracy **Reliability:** **Pros:** - Time-tested method (centuries old) - Reliable for karat determination - Inexpensive to perform - Confirms minimum purity - Works without electricity **Cons:** - Slightly destructive (tiny scratch) - Acid handling requires care - Can stain items if careless - Subjective interpretation sometimes - Less precise than XRF **When Goldealers Uses Acid:** - XRF result seems incorrect - Suspect plating or fake - Customer requests verification - Quality control spot-checks - Very old or unusual items **Accuracy Level:** - Within 1-2 carats typically - 14ct-16ct range detectable - Not as precise as XRF - Sufficient for scrap valuation - Good secondary confirmation > Acid testing requires careful handling. Strong acids can burn skin and damage surfaces. Professional dealers use acids safely with proper training and equipment. ## Electronic Gold Testers Handheld devices using conductivity principles. ### How Electronic Testers Work **Technology:** **Operating Principle:** - Measures electrical conductivity - Applies test solution to metal - Small electrical current passed - Conductivity varies by purity - Device interprets reading - Displays estimated karat **Usage:** - Apply test gel to item - Place probe on gel - Press button - Reading appears (e.g., "18K") - Wipe off gel - Item undamaged **Types:** - Gel-based testers (common) - Ultrasonic testers (newer) - Thermal conductivity testers (rare) - Various brands and models ### Pros and Cons **Advantages:** **Non-Destructive:** - No scratch needed - Removes gel easily - Item pristine after test - Customer-friendly **Portable:** - Battery operated - Handheld - Good for mobile dealers - Convenient at shows/markets **Quick:** - Result in seconds - Faster than acid - Multiple items tested fast **Disadvantages:** **Accuracy Issues:** - Can be fooled by plating - Alloy composition affects reading - May misread by 1-2 karats - Not as reliable as XRF **Limitations:** - Surface must be clean - Gel can dry out - Calibration can drift - Less precise with mixed alloys **Cost vs Performance:** - Good testers: £200-500 - Cheap testers: unreliable - XRF more accurate for investment **Goldealers' View:** - Useful for quick screening - Not relied on for final valuation - Supplement to XRF/acid - Handy for preliminary checks > Electronic testers are popular with hobbyists and small dealers, but professional buyers like Goldealers prefer XRF or acid for definitive testing. ## Magnet Test Simple but effective screening tool. ### How It Works **Basic Physics:** **Magnetic Properties:** - Gold is not magnetic (diamagnetic actually) - Silver not magnetic - Platinum not magnetic - Steel/iron strongly magnetic - Some alloys magnetic **Testing Method:** - Strong magnet (neodymium recommended) - Bring near item - If attracted = not gold/silver/platinum - If not attracted = possibly precious metal - Quick elimination test **What It Proves:** **Positive Magnetic Response:** - Definitely not pure gold/silver/platinum - Could be steel core with plating - Ferrous base metal - Immediate fail - No further testing needed **Negative (No Attraction):** - Might be gold/silver/platinum - Or might be copper/brass (also non-magnetic) - Or could be aluminium/zinc - Doesn't prove it IS precious metal - Further testing required ### Practical Application **Goldealers Usage:** **First Quick Check:** - Pull out magnet - Test all items - Remove obvious fakes immediately - Saves testing time on steel/iron - Quick screening **Examples:** - Costume jewellery with steel clasp - Gold-plated steel chains - Fake "gold" coins - Steel core rings **Limitations:** - Many fakes also non-magnetic - Brass looks like gold, not magnetic - Test alone insufficient - Good negative screen (rules out ferrous) - Poor positive confirmation > The magnet test is free, instant, and eliminates obvious fakes. Every dealer has a magnet for this reason. But passing the magnet test doesn't mean an item is gold – just that it's not steel. ## Specific Gravity (Density Test) Physics-based authentication for bars and coins. ### Principle **Density of Gold:** **Pure Gold:** - Density: 19.32 g/cm³ - Very dense (heavy for size) - Distinctive characteristic - Hard to fake accurately **Alloys:** - 9ct: ~11-12 g/cm³ - 14ct: ~13-14 g/cm³ - 18ct: ~15-16 g/cm³ - 22ct: ~17-18 g/cm³ - Varies with alloying metals **Common Fakes:** - Brass: ~8.5 g/cm³ (too light) - Lead: ~11.3 g/cm³ (too light) - Tungsten: ~19.3 g/cm³ (close! Clever fake material) - Steel: ~7.9 g/cm³ (much too light) ### Testing Method **Archimedes Principle:** **Equipment:** - Precise scale - Beaker of water - Suspension setup (string or clip) - Calculator **Procedure:** 1. Weigh item in air (mass M) 2. Suspend item in water 3. Weigh item submerged (appears lighter - buoyancy) 4. Calculate volume from weight difference 5. Density = M ÷ Volume 6. Compare to known gold densities **Example:** - Gold bar weighs 100g in air - Weighs 95g in water (5g buoyancy) - Volume = 5cm³ (1g water = 1cm³) - Density = 100 ÷ 5.17 = 19.34 g/cm³ - **Matches gold! Likely authentic.** ### When Used **Typical Applications:** **Bullion Verification:** - Gold bars (especially large ones) - Coins suspected of being fake - High-value items - When XRF unavailable - Suspicious weight for size **Detection of Tungsten Fakes:** - Tungsten density very close to gold - XRF detects easily (different element) - Density alone might not catch tungsten - Use multiple methods **Limitations:** - Time-consuming - Requires careful measurement - Only works for solid uniform items - Hollow/filled items misleading - Jewellery with stones problematic **Goldealers' Use:** - Rarely needed with XRF available - Occasionally for large bar verification - Secondary check on suspicious items - Mostly for our peace of mind [Selling unhallmarked gold (requiring testing)](/knowledge/gold/can-sell-gold-not-hallmarked) ## Fire Assay Ultimate precision for refinery-level testing. ### What It Is **Definition:** **Process Overview:** - Destructive analytical technique - Sample melted with lead and flux - Base metals oxidise away - Pure gold/silver bead remains - Weighed for exact purity - Industry gold standard (pun intended) **Accuracy:** - Precise to 0.001% possible - Definitive purity determination - Used by refineries - Hallmarking assay offices - Settlement of large transactions **Destructive Nature:** - Sample destroyed - Small portion of item taken - Or entire small item melted - Not used for customer jewellery assessment - Reserved for batch refining ### When Applied **Usage Scenarios:** **Refinery Assay:** - When Goldealers sends scrap to refinery - Sample taken from melted batch - Determines exact purity of lot - Final settlement based on assay - Extremely accurate **Hallmarking:** - Assay Offices use fire assay - Verify items before hallmarking - Destructive sample taken - Legal requirement for hallmarks - Authoritative purity certification **Large Transaction Settlement:** - £100,000+ gold bar purchases - Between refineries/banks - When absolute certainty needed - Contract requirement sometimes **Goldealers Relation:** - We don't perform fire assay in-house - Our refinery partners do - For final batch settlement - Confirms our XRF testing was accurate - Rarely significant discrepancy > Fire assay is the most accurate test for gold purity, but it's impractical for everyday use because it destroys the sample. XRF provides excellent accuracy without destruction. ## Multi-Method Approach Why professionals use multiple tests. ### Layered Verification **Goldealers' Standard Process:** **Step 1: Visual & Hallmark** - Quick assessment - Identify obvious issues - Note hallmarks - Initial classification **Step 2: Magnet Test** - Instant fake detection - Remove ferrous items - 5 seconds per item - First elimination **Step 3: XRF Testing** - Primary testing method - Accurate composition - Non-destructive - 30 seconds per item - High confidence result **Step 4: Verification (if needed)** - Acid test if XRF questionable - Multiple XRF points if suspicious - Customer discussion if unclear - Professional judgement **Step 5: Documentation** - Record all results - Photograph items - Note any anomalies - Audit trail ### Why Multiple Methods **Redundancy and Accuracy:** **Each Test's Strength:** - Hallmarks: Quick pre-identification - Magnet: Fast fake elimination - XRF: Accurate, non-destructive composition - Acid: Traditional verification - Density: Physical property check **Catching Sophisticated Fakes:** - Gold-plated tungsten: density close, but XRF reveals - Brass plated with thick gold: magnet passes, but XRF detects - Fake hallmarks: visual notices inconsistencies - Layer ed construction: multiple XRF points reveal **Customer Confidence:** - Multiple tests = thorough - Transparent process - Clearly not guessing - Professional approach - Fair to all parties > Professional dealers like Goldealers invest in multiple testing methods and skilled staff. This layered approach ensures accuracy and fairness for both buyer and seller. ## Frequently Asked Questions **Q: How do gold dealers test if gold is real and what carat it is?** A: Dealers use a combination of methods to test gold. First, they check for official hallmarks. Then they often use devices like XRF analysers that can scan the metal and instantly report its composition. Traditional acid tests are also used – a small rubbing of the gold is exposed to nitric acid to confirm its karat. Other tools include electronic testers and simple magnet checks (real gold isn't magnetic). Goldealers primarily uses non-destructive testing (like XRF), ensuring accurate results without damaging your item. **Q: What is XRF testing and why do dealers use it?** A: XRF (X-ray Fluorescence) is a high-tech method that shoots X-rays at metal to identify its composition. It's fast (results in seconds), accurate (to 0.1%), non-destructive (no damage to item), and works on all precious metals. Goldealers and professional dealers use XRF because it provides laboratory-grade precision without scratching or altering items. **Q: Can gold testing damage my jewellery?** A: It depends on the method. XRF testing causes zero damage – it's completely non-destructive. Acid testing requires a tiny scratch on an inconspicuous area to create a test streak, causing minimal damage. Magnet testing causes no damage. At Goldealers, we primarily use XRF to keep your items pristine. **Q: How accurate are those handheld electronic gold testers?** A: Moderately accurate if good quality, but not as reliable as XRF or acid tests. They can be fooled by thick plating or unusual alloys, and may misread purity by 1-2 karats. Professional dealers use them for quick screening but verify with more accurate methods for final valuations. **Q: Can dealers tell if gold is fake just by looking?** A: Experienced dealers can spot obvious fakes visually (weight, colour, hallmarks, wear patterns), but cannot definitively authenticate by sight alone. Even experts need technical testing to be certain. Visual inspection is just the first step before scientific testing. **Q: Why do you need to test hallmarked gold?** A: Unfortunately, fake hallmarks exist, hallmarks can be on plated items, and genuine hallmarks sometimes wear off or are on parts that were replaced. Testing verifies the metal matches its markings. Reputable dealers always test regardless of hallmarks to ensure accurate pricing. ## Next Steps Understanding how gold is tested professionally helps you appreciate the care taken in valuation. Goldealers' multi-method approach, led by XRF technology, ensures accurate, fair testing of all items. **Useful Resources:** - [Detailed XRF explanation](/knowledge/testing/what-is-xrf-testing) - [DIY gold testing methods](/knowledge/testing/how-to-test-gold-at-home) - [Understanding purity and hallmarks](/knowledge/gold/gold-purity-hallmarks) **Sell your gold confidently knowing Goldealers uses professional testing methods.** --- *Published by Goldealers Ltd · https://goldealers.co.uk/knowledge/testing/how-is-gold-tested-by-dealers*