Silver Doré Bars are semi-refined precious metal bars containing silver as the primary component, along with varying amounts of gold and trace base metals such as copper, lead, or zinc. They are produced as an intermediate product during the mining and initial smelting of silver and gold ores.
Unlike fully refined silver bullion, silver doré bars are not investment-grade. They are intended for further refining at accredited refineries, where silver, gold, and other valuable elements are separated into high-purity metals.
Silver doré bars play a critical role in the global precious metals supply chain and serve as the primary feedstock for silver refineries worldwide.
Typical Purity & Grade Range
Silver doré bars do not have fixed purity. Composition depends on ore type, mining method, and smelting route.
| Component | Typical Range |
|---|---|
| Silver (Ag) | 50% – 98% |
| Gold (Au) | 0.1% – 20% |
| Copper (Cu) | 0.5% – 5% |
| Lead (Pb) | Trace – 2% |
| Zinc (Zn) | Trace |
| Other elements | ppm – % |
Common Doré Grade Bands:
• Low-grade doré: 50–70% Ag
• Medium-grade doré: 70–90% Ag
• High-grade doré: 90–98% Ag
High-gold silver doré is common in polymetallic deposits.
Chemical Composition Overview
| Element | Role |
|---|---|
| Silver (Ag) | Primary precious metal |
| Gold (Au) | Valuable secondary metal |
| Copper (Cu) | Smelting impurity |
| Lead (Pb) | Common from Pb–Zn ores |
| Zinc (Zn) | Trace element |
| Sulfur (S) | Residual |
| Selenium / Tellurium | Trace |
Physical Properties
| Property | Typical Value |
|---|---|
| Color | Dull white, grayish, or yellowish |
| Density | 9.5 – 11.5 g/cm³ (composition dependent) |
| Surface Finish | Rough, porous, cast |
| Magnetic Behavior | Non-magnetic |
| Homogeneity | Non-uniform |
Visual appearance varies significantly between production sources.
Mechanical Properties
Silver doré bars are not engineered structural materials.
| Property | Characteristic |
|---|---|
| Hardness | Variable |
| Brittleness | Moderate |
| Machinability | Poor |
| Load-bearing use | None |
Metallurgical Structure & Behavior
• Multi-phase Ag-based alloy
• Entrapped gold inclusions
• Base-metal intermetallics
• Porosity from smelting and casting
✔ Composition varies within the bar
✔ Impurity segregation is common
✔ Cooling rate affects grain structure
Refining & Processing Properties
Production Route:
• Ore crushing and grinding
• Concentration (flotation / leaching)
• Smelting
• Casting into doré bars
Refining Methods:
• Electrorefining (silver anodes)
• Nitric acid dissolution
• Parkes process (lead-based recovery)
• Miller / Wohlwill processes (gold separation)
Final refining produces silver with purity levels of 99.9% – 99.99%.
Available Forms
✔ Rectangular cast doré bars
✔ Irregular ingots
✔ Typical weight: 5 kg – 30 kg
✔ Mine-stamped identification
Applications
Primary: Feedstock for silver refineries
Secondary: Recovery of gold by-product
Downstream: Conversion into LBMA silver bars, industrial silver, coins, and medallions
Advantages
✔ High silver concentration compared to raw ore
✔ Easier transport and storage
✔ Cost-efficient refinery input
✔ Enables simultaneous gold recovery
✔ Universally accepted by refineries
Limitations
⚠ Not investment-grade
⚠ Variable purity
⚠ Requires assay and refining
⚠ Not suitable for direct retail trading
Silver Doré vs Refined Silver
| Feature | Silver Doré | Refined Silver |
|---|---|---|
| Purity | 50–98% | ≥99.9% |
| Refining Needed | Yes | No |
| Surface Finish | Rough | Smooth |
| Investment Grade | ❌ | ✔ |
| Certification | Mine assay | LBMA / Mint |
Why Choose Silver Doré Bars
Silver doré bars are selected when silver is produced at mine or smelter level, off-site refining is planned, transport efficiency is required, and gold–silver separation is needed. While unsuitable for direct investment, silver doré bars are essential to the global silver supply chain.