How to Extract Gold From Ore With Caustic Soda & Mercury

Mercury can be used to extract raw gold from ore.

Gold occurs in many forms in nature. The gold nuggets or gold sands of gold rush fame are actually quite rare, and most gold occurs in combination with copper and silver in regular ore, which is mined the same way as other metals. For gold sand, as well as for some types of ore, gold is extracted using mercury.

Things You'll Need

• Equipment to crush the ore to a fine powder
• Washing pan to clean the ore
• Barrel amalgamator, which you can make from a cement mixer, or amalgamation plates
• 5 times the amount of mercury as the amount of gold in the ore batch
• 3 to 4 pounds of caustic soda per ton of ore
• Chamois cloth or canvas
• Nitric acid
• Retort for heating nitric acid and mercury amalgam

Instructions

1. Insert the crushed and washed ore in the barrel amalgamator.

2. Add 5 times the amount of mercury as there is gold in the batch to be processed. Add 3 to 4 pounds of caustic soda per ton of ore. The caustic soda is only to keep the gold and mercury clean. It does not have a chemical function.

3. Mix the ore, mercury, and soda thoroughly for several hours.

4. Collect the amalgam of gold and mercury after they have been thoroughly mixed.

5. Remove the excess mercury by squeezing it though damp chamois or canvas over a table. This leaves a hard lump of amalgam of gold and mercury.

6. Dissolve the amalgam in diluted nitric acid in the glass retort. Mercury and silver are dissolved leaving the gold.

7. Boil off the nitric acid, which also boils off the mercury.

8. Capture the mercury fumes and condense them to reuse the mercury.

9. Recover the gold from the retort.

Tips & Warnings

• If clean gold and clean mercury come into contact, the gold will be absorbed in the mercury.

• Mercury compounds are poisonous. Always wear gloves and use a well-ventilated work environment when working with mercury.

• Nitric acid fumes can be lethal if breathed. Exercise caution.

• Caustic soda can scour the skin if not handled with care.

• There are always risks of body damage when working with heavy equipment and processing rocks.

• Unless the process is applied under the control of chemists in a controlled environment, the results will be variable and result in gold of different composition and purity.

References

• Arizona Department of Mines and Mineral Resources: Treating Gold Ores by Amalgamation
• Nevada Outback Gems: Assaying Gold and Silver Ores: Fire Assaying and Other Testing Methods
• Worstpolluted: Top six environment threats: Mercury