In gold and silver refining, a fraction of a gram or a minor error in melting loss calculation can wipe out your operating margin. Whether processing old jewellery scrap, kuccha dhalai bars, or refinery sweeps, maintaining audit-proof lot accounting is what separates profitable refineries from those suffering silent inventory leakage. Here is the complete operational guide to calculating yield, tracking melting losses, and settling running metal ledgers with complete precision.
The Real Anatomy of a Precious Metal Refining Lot
Unlike a bullion trader who buys and sells finished bars at spot rates, a refinery is an industrial transformation facility. Customers—jewellers, bullion dealers, pawnbrokers, and scrap collectors—deposit unrefined metal with varying impurities, solder, and enamel. They expect either certified 999.0+ fine pure metal return or cash settlement, minus your refining charges (ghatai/dhalai) and recorded melting losses.
Every refining lot must progress through a closed, tamper-resistant lifecycle:
- Inward Weighing & Lot Creation: Recording the raw gross weight on a calibrated 3-decimal scale (0.001g precision), noting visual purity estimates, and generating an Inward Voucher.
- Melting (Dhalai) & Slag Removal: Heating the scrap in an induction or gas furnace with fluxes (borax/nitre) to homogenize the metal into a solid bar. Slag is skimmed off, and the post-melt bar is weighed.
- Melting Loss Verification: The difference between gross raw intake and the melted bar weight represents burn-off, enamel, dirt, and oxide slag. Both the refiner and customer must agree on this loss before chemical processing.
- Assay Purity Sampling (Tunch): Taking sample drillings or dip samples for fire assay (cupellation) or energy-dispersive XRF spectrometer analysis to establish exact fine metal percentage (e.g., 84.65% Au).
- Fine Yield Recovery: Calculating net 999 fine metal yielded from the assayed bar weight.
- Refining Fee Deduction & Settlement: Deducting refining fees (either as a metal weight deduction or a fixed cash charge per kg) and crediting the deliverable fine metal to the customer's running ledger.
Core Mathematical Formulas for Lot Accounting
Standardize these three formulas across your refinery intake desk to eliminate verbal estimates and calculator discrepancies:
1. Melting Loss Formula:
Melting Loss (g) = Gross Inward Weight - Melted Bar Weight
Melting Loss % = (Melting Loss ÷ Gross Inward Weight) × 100
2. Net 999 Fine Metal Yield Formula:
Fine Metal Yield (g) = (Melted Bar Weight × Assay Purity %) ÷ 100
(For 999 fine benchmark: Fine Yield 999 = Fine Metal Yield ÷ 0.999)
3. Deliverable Customer Settlement:
Deliverable Fine (g) = Fine Metal Yield - Metal Refining Charge (g)
(If fee is paid in cash: Cash Fee = Melted Bar Weight in kg × ₹ Fee/kg)
A Real-World Mandi Example
Consider a jeweller who deposits old 20K and 22K scrap jewellery at your refinery counter:
- Gross Inward Weight: 1,250.000 g
- Post-Melting Bar Weight: 1,218.500 g
- Melting Loss: 31.500 g (2.52% burn-off / stones / impurities)
- XRF / Fire Assay Purity: 88.40% Gold (884.0 purity)
Now, calculate the fine recovery:
Standard 999 Fine Equivalent = 1,077.154 ÷ 0.999 = 1,078.232 g
If your refining charge is ₹800 per kilogram of melted bar, the processing fee is:
The customer's account receives an immediate credit of 1,078.232 g of 999 Gold in their running fine metal balance, and a debit of ₹974.80 in their cash ledger. When they collect physical 999 minted bars or request RTGS bank payout at the day's market rate, those vouchers offset these running balances instantly.
Handling Silver Separation and Byproduct Recovery
Gold scrap frequently contains 5% to 15% silver alloy. In large lots, unrecorded silver recovery is a primary source of audit disputes. For instance, in a 5,000g gold lot with 8% silver content, there is 400g of pure silver recovery.
A professional refinery records secondary metal recovery as a separate credit line in the customer's silver ledger. Separating gold and silver accounts prevents cross-contamination of unit prices and keeps tax documentation straightforward.
Why Traditional Paper Registers Fail at Scale
When refineries handle dozens of lots daily across multiple furnaces, manual paper slips break down quickly:
- Disconnected Stages: The melting supervisor writes one slip, the lab technician writes another assay certificate, and the cashier holds a third ledger. Reconciling them at end-of-day takes hours.
- Disputed Melting Losses: Without an immediate printed or digital intake voucher signed at the scale, customers may claim their ornaments had less enamel or dirt.
- Running Balance Confusion: Customers rarely take delivery of exact fractional grams. Partial deliveries leave floating gram balances (e.g., 14.382g remaining) that get lost in handwritten bahi khata notebooks.
How Refinery Master Automates Lot Accounting
Refinery Master is built specifically for Indian precious metal refiners to solve this exact challenge:
- End-to-End Lot Lifecycle: Track intake, melting loss, assay test results, and yield in a single digital lot card.
- Dual Currency Ledgers: Real-time tracking of running cash balances (₹) and pure fine weight (g) per customer with 3-decimal accuracy.
- Sequential Voucher Numbering: Generates tamper-resistant, audit-compliant sequential vouchers for intake, refining loss, exchange, and delivery.
- 100% Offline-First Architecture: Runs on a local SQLite database on your Android tablet or phone. Operates continuously during power cuts or network drops without relying on cloud servers.
Take control of your refinery floor and ensure every milligram is accounted for. Try Refinery Master free for 30 days with zero credit card commitment.