Advanced multi-stage pyrometallurgical and hydrometallurgical processes delivering 99.99% pure gold bullion — the highest achievable international standard.
Gold refining is the process of purifying raw or impure gold — doré bars, alluvial gold, scrap jewellery, or mining concentrate — into investment-grade, high-purity bullion. Impurities including silver, copper, lead, zinc, and other base metals are systematically removed through controlled chemical and thermal processes.
At Oasis Gold Refinery we employ a two-stage approach: the Miller Chlorination Process for high-speed primary purification to 99.5%, followed by the Wohlwill Electrolytic Process to achieve the final 999.9 fine gold standard (99.99% purity) — the benchmark recognised by the London Bullion Market Association (LBMA) and central banks worldwide.
By an estimated measure, two-thirds of all the gold ever refined in history has passed through the Miller process alone. By combining it with Wohlwill electrolysis we deliver both speed and the highest possible purity — in one seamless workflow at our Kampala facility.
We use the same world-class methods employed by Rand Refinery and the world's largest gold producers — Miller chlorination followed by Wohlwill electrolysis.
Developed and patented in London in 1867 by Francis Bowyer Miller, the Miller Process is the fastest and most widely used gold refining method in the world.
Impure gold is smelted until fully molten in a high-temperature furnace. Gaseous chlorine is then blown into the liquid metal. Base metal impurities — silver, copper, zinc, lead — react with the chlorine to form chloride compounds that rise to the surface as a slag layer. These are physically removed, leaving behind gold at approximately 99.5% purity.
The process is rapid, scalable, and economical — ideal for the high-volume artisanal and small-scale mining (ASM) gold that characterises Uganda's mining sector.
Developed by Emil Wohlwill in Hamburg in 1874, the Wohlwill Electrolytic Process is the gold industry's premier method for achieving the absolute highest purity: 999.9 fine (99.99%) — the LBMA Good Delivery standard accepted by central banks and international bullion markets worldwide.
Gold from the Miller stage is cast into anode plates and immersed in an electrolyte solution of hydrochloric acid and gold chloride. A direct electrical current drives gold ions from the anode, which deposit as ultra-pure gold crystals on the cathode, while all remaining impurities — including platinum group metals — remain in the electrolyte or anode slime for separate recovery.
The deposited gold crystals are then washed, dried, melted, and cast into certified 999.9 fine gold bars — ready for trade, export, or investment.
Every parcel follows a strict, fully documented five-step chain of custody — complete transparency from first weighing to final delivery.
Gold is received, weighed on certified scales, and assigned a unique lot ID. A witnessed receipt is issued on the spot.
Fire assay or XRF testing determines the exact gold content and identifies all impurities present before any processing begins.
Material is smelted until molten, then chlorine is blown through to drive off base metals. Output: 99.5% pure gold.
Miller-refined gold is electrolytically refined to 999.9 fine — ultra-pure gold crystals deposited on cathode plates.
Pure gold is melted, cast into bars or granules, assay-certified at 999.9 fine, and prepared for collection, trading or export.
| Method | Purity Achieved | Speed | Best For | Oasis Usage |
|---|---|---|---|---|
| Smelting / Cupellation | 90–95% | Fast | Pre-treatment & silver removal | ✓ Stage 0 |
| Miller Chlorination | Up to 99.5% | 4–6 hrs | High-volume primary refining | ✓ Stage 1 |
| Wohlwill Electrolysis | 99.99% (999.9 fine) | 24–48 hrs | LBMA investment-grade bullion | ✓ Stage 2 |
| Aqua Regia (Acid) | Up to 99.99% | Slower | Small batches, jewellery scrap | ✓ On request |