How Banks Calculate Gold Purity & Appraisal Deductions
Appraisal Golden Rules
- ✔Gross Weight ≠ Loan Weight: The total weight on your kitchen scale includes stones, wax, enamel, and solder. The bank calculates credit strictly on Net Pure Gold Weight.
- ✔Stones Count as Zero: Diamonds, rubies, pearls, and cubic zirconia receive zero valuation credit under standard gold loan policies.
- ✔Minimum Acceptable Purity: Most institutional lenders require at least 18 Karat (75.0% pure) gold. Items below 18K are generally declined.
1. The Three Tiers of Weight in Gold Appraisal
When you take jewellery to a lender, the appraiser identifies three distinct weight metrics:
- Gross Weight: The total physical weight of the entire piece as placed onto a calibrated precision balance.
- Tare Weight (Deductions): The combined weight of all non-gold components (gemstones, enameling, lac/wax filling, threads, and non-precious pins).
- Net Weight: Gross Weight minus Tare Weight. This represents the true gold alloy weight.
2. Common Appraisal Deductions Explained
Borrowers are often surprised when their 40-gram necklace is credited as only 28 grams of gold. Here is why those deductions happen:
| Component | Typical Weight Share | Lender Treatment | Reasoning |
|---|---|---|---|
| Lac / Wax Core (लाख) | 15% – 35% in bangles & heavy chokers | 100% Deducted | Resin filler burns away upon melting; zero bullion value. |
| Diamonds & Gems | 5% – 30% depending on design | 100% Deducted | Bank appraisers cannot verify secondary market gem grades. |
| Enamel / Meenakari | 2% – 8% | Estimated & Deducted | Glass/mineral coating has no bullion recovery value. |
| Solder Metal (टांका) | 2% – 5% | Fineness Adjusted | Cadmium or zinc solder lowers overall karat purity. |
3. How Purity Is Tested: Touchstone vs Karatmeter
Lenders use three primary metallurgical appraisal techniques:
A. The Touchstone (Kasauti) & Acid Test
The traditional method used by bank jewelers. The ornament is gently rubbed against a black slate stone (siliceous rock), leaving a microscopic streak of gold. Standard nitric acid solutions (formulated for 18K, 22K, and 24K) are applied to the streak. Because gold is chemically noble and non-reactive, the resistance of the mark reveals the exact karat bracket.
B. Electronic X-Ray Fluorescence (XRF) Karatmeter
Modern NBFC branches (e.g. Muthoot, IIFL) feature state-of-the-art non-destructive XRF spectrometers. The item is placed inside a sealed testing chamber where targeted X-rays excite the metal's atoms. The returning fluorescence energy profile calculates the percentage breakdown of gold, copper, silver, and zinc within 30 seconds with 99.9% precision.
C. Specific Gravity (Archimedes' Hydrostatic Test)
For thick, hollow ornaments or items with suspected interior cavities, appraisers weigh the object in air and then fully submerged in water. Because pure gold has a distinct density of 19.32 g/cm³, Archimedes' displacement formula detects any hidden base metals (like tungsten or copper cores) without scratching the surface.
4. Step-by-Step Worked Example: Appraising a 50g Kundan Necklace
Let's follow a realistic appraisal for an elaborate 50-gram wedding necklace:
Step 1: Gross Weight Measurement
Total scale weight: 50.00 grams
Step 2: Appraiser Deductions (Tare)
- Kundan stones & pearls: 7.50 grams
- Lac / resin core in beads: 4.50 grams
- Dori thread & metallic cord: 3.00 grams
Total Deductions: 15.00 grams
Step 3: Net Eligible Gold Weight
50.00g - 15.00g = 35.00 grams
Step 4: Purity Testing
Tested Karat: 22K (91.6% Pure)
Step 5: Valuation & Loan Eligibility (at ₹7,000/g 22K rate, 75% LTV)
Market Valuation = 35g × ₹7,000 = ₹2,45,000
Sanctioned Loan (75% LTV) = ₹2,45,000 × 0.75 = ₹1,83,750
5. Tips to Maximize Your Loan Amount Before Visiting a Bank
- Choose Solid Jewellery: Plain gold chains, solid bangles, and simple rings have minimal tare deductions (0% to 2%), giving you the highest cash disbursal per gram.
- Bring Purchase Invoices & BIS Hallmarking: Having the original hallmarked invoice proves stone weight breakdown and prevents aggressive over-deductions by the bank's appraiser.
- Request an Itemized Appraisal Memo: Always review the appraiser's written deduction slip before consenting to sign loan documents.
Estimate Your Melt vs Pawn Value
Compare what your jewellery is worth if melted as scrap versus the cash loan you can obtain through our dedicated Pawn vs Melt calculator.
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