A Gold Doré Bar is a semi-refined precious metal bar produced at mines or initial processing facilities. It contains gold alloyed with silver and minor impurities and represents an intermediate product between mining and full refining.
Doré bars are not investment-grade bullion. They are manufactured strictly as refinery feedstock and must undergo further chemical refining before being converted into bullion bars, coins, or industrial gold.
Typical Purity & Grade Range
Gold doré bars do not have a fixed purity. Composition varies depending on ore source, recovery method, and smelting conditions.
| Component | Typical Range |
|---|---|
| Gold (Au) | 50% – 95% |
| Silver (Ag) | 5% – 45% |
| Base metals (Cu, Pb, Zn, Fe) | < 1 – 3% |
| Trace elements (Se, Te, Hg) | ppm – % |
Common Doré Grade Bands
✔ Low-grade doré: 50 – 70% Au
✔ Medium-grade doré: 70 – 85% Au
✔ High-grade doré: 85 – 95% Au
✔ Very high-grade doré (>95% Au) — rare and near refinery bullion
Metallurgical Behavior & Structure
Microstructure:
• Multi-phase Au–Ag alloy matrix
• Entrapped base-metal inclusions
• Casting porosity and segregation
Metallurgical Characteristics:
✔ Not a single-phase alloy
✔ Composition varies within the bar
✔ Requires chemical refining prior to use
Strengthening Mechanisms:
❌ No intentional strengthening
✔ Hardness influenced by silver and copper content
✔ Cooling rate affects grain size and casting structure
Doré bars are functional transport forms, not engineered alloys.
Production & Processing Route
How Doré Bars Are Made:
• Ore crushing and grinding
• Gold recovery (CIP, CIL, flotation, amalgamation)
• Smelting of concentrate
• Casting into doré bars
Refining Methods:
• Miller process (chlorination)
• Wohlwill electrolytic refining
• Aqua regia refining
Available Forms
✔ Rectangular cast bars
✔ Rough-edged ingots
✔ Typical weight: 5 – 25 kg per bar
✔ Mine-stamped identification marks
Applications
Primary Use:
• Feedstock for gold refineries
Secondary:
• International precious metal trade
• Conversion into LBMA Good Delivery bars, coins, bullion, and industrial gold
Advantages of Doré Bars
✔ Easier transport than raw ore
✔ High precious-metal concentration
✔ Lower refining cost vs untreated ore
✔ Accepted by all major global refineries
Limitations
⚠ Not investment-grade
⚠ Variable purity and composition
⚠ Requires assay before sale
⚠ Not tradable by retail investors
Doré Bar vs Bullion Bar
| Feature | Doré Bar | Bullion Bar |
|---|---|---|
| Purity | 50 – 95% | ≥ 99.5% |
| Refining Required | Yes | No |
| Investment Grade | ❌ | ✔ |
| Surface Finish | Rough | Smooth |
| Certification | Mine assay | LBMA / Mint |
Why Choose Doré Bars?
Doré bars are selected when:
✔ Gold is produced at mine level
✔ Refining will occur off-site
✔ Transport efficiency is required
✔ Large-scale precious-metal processing is involved
In summary: A Gold Doré Bar is a semi-refined Au–Ag alloy typically containing 50–95% gold, produced as an intermediate product between mining and full refining. While unsuitable for direct investment or jewelry use, doré bars are essential to the global gold supply chain, serving as the raw material for investment-grade bullion, coins, and industrial gold products.