Laboratory Analysis
Gold Assay Laboratory Process
Understanding institutional-grade gold purity testing, certification, and the analytical chemistry behind every assay report.
The Assay Process
Gold assay is the definitive process for determining the purity and composition of gold. At Nile Precious Metals, we employ a multi-method approach that combines non-destructive XRF analysis with destructive fire assay to deliver the highest confidence results for institutional buyers.
Every dore bar we export undergoes both methods: XRF for rapid surface composition analysis, and fire assay for core-sample purity verification. This dual-method approach eliminates the risk of surface-plated fraud and ensures reported purity is representative of the entire bar.
Why Dual Assay Matters:
- XRF detects surface composition only (0.01mm depth)
- Fire assay verifies core purity through complete melt
- Dual results cross-validated for 99.99% confidence
- Required by LBMA-affiliated refiners for acceptance
Technical Specifications
- ✓XRF Precision: ±0.1% for 24K gold
- ✓Fire Assay Accuracy: 99.99% confidence
- ✓Sampling: Random representative per batch
- ✓Lab Accreditation: ISO 17025
- ✓Gravimetric Weight: 0.001g precision
- ✓Chain of Custody: Tamper-evident sealed
4-Stage Assay Pipeline
XRF Scan
Non-destructive X-ray fluorescence analysis. Measures surface gold, silver, and base metal composition in seconds.
Core Sampling
Representative samples drilled from multiple points across the bar. Ensures homogeneity testing of the entire bar.
Fire Assay
Sample melted with flux in a cupel at 1100°C. Gold separates from all base metals — the definitive purity test.
Certification
Certificate of Analysis issued with both XRF and fire assay results, weight, dimensions, and chain-of-custody reference.
ISO 17025 Accreditation
ISO 17025 is the international standard for testing and calibration laboratories. Labs holding this accreditation have demonstrated their ability to produce technically valid results with traceable measurement standards. Our assay partners operate under ISO 17025 accreditation, ensuring every certificate of analysis is internationally recognized.
What ISO 17025 Requires
- ✓Validated test methods with uncertainty budgets
- ✓Calibrated equipment with traceability
- ✓Proficiency testing programs
- ✓Documented quality management system
Certificate of Analysis
- ✓XRF result with ±0.1% precision
- ✓Fire assay result with confidence level
- ✓Bar weight, dimensions, serial number
- ✓Lab accreditation reference and date
Frequently Asked Questions
What is the difference between XRF and fire assay?
XRF (X-Ray Fluorescence) is a non-destructive surface analysis that measures elemental composition. Fire assay (cupellation) is a destructive process that melts the sample to separate gold from all other metals, providing the most accurate purity measurement. Both are used together for maximum confidence.
How accurate is fire assay for gold?
Fire assay is considered the gold standard for purity testing, with accuracy to 99.99% confidence level. It can detect gold content to within 0.005% for high-purity samples.
Why is ISO 17025 important for gold assay?
ISO 17025 accreditation ensures the lab operates with validated methods, calibrated equipment, and quality management systems. Without it, assay results may not be accepted by LBMA-affiliated refiners or institutional buyers.
Can I receive a copy of the assay report before purchasing?
Qualified institutional buyers can request assay reports for specific lots. Contact our technical desk with your requirements and we will provide documentation for review.
Request Assay Report
Every institutional shipment includes a comprehensive dual-assay report. Contact our technical desk for specifications and sampling methodology.