Gold is one of the most precious metals in the world, and it is extracted and purified in labs using various techniques. In this article, we will discuss the process of extracting and purifying gold in a laboratory setting.

Step 1: Preparation

Before the actual extraction and purification process can begin, the gold-containing ore or material must be prepared.

This involves crushing the material into small pieces and then grinding it into a fine powder. This helps to expose more of the gold particles, making it easier to extract.

Step 2: Chemical Leaching

Chemical leaching is one of the most common methods used to extract gold from ore. In this process, a chemical solution is used to dissolve the gold particles.

The most commonly used chemical for this process is cyanide. Cyanide is a highly toxic chemical, and extreme caution must be taken when handling it.

The gold-containing ore is mixed with a cyanide solution in large tanks. The mixture is stirred, and the cyanide slowly dissolves the gold particles.

The gold is then extracted from the solution using a process called adsorption. This involves passing the solution over activated carbon, which attracts and holds the gold particles.

Step 3: Elution

Once the gold particles have been adsorbed onto the activated carbon, they must be eluted or removed. This is done by washing the activated carbon with a caustic solution of sodium hydroxide and cyanide. The gold particles are then dissolved in the solution and collected.

Step 4: Electro-winning

The gold-containing solution obtained from the elution process is then subjected to electro-winning. This involves passing an electric current through the solution, which causes the gold particles to be deposited onto a cathode. The cathode is then removed and the gold particles are scraped off.

Step 5: Refining

The gold obtained from the electro-winning process is not yet pure and must be further refined. This is done using a process called smelting.

In this process, the impurities in the gold are melted away using a high-temperature furnace. The pure gold is then cast into bars or other shapes for storage or further processing.

Step 6: Assaying

Assaying is the process of determining the purity and quality of the gold. This is done by analyzing a small sample of the gold using various techniques, including X-ray fluorescence, fire assay, and atomic absorption spectroscopy. The results of the assay are used to determine the exact percentage of gold in the sample.

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Step 7: Final Purification

The final step in the process is to purify the gold even further. This is done using a process called refining. In this process, the gold is melted and then treated with various chemicals to remove any remaining impurities. The resulting gold is then cast into bars or other shapes for storage or sale.

Some important data points related to gold extraction and purification:

  1. The average concentration of gold in the Earth’s crust is about 0.005 parts per million (ppm).
  2. Gold ore is typically mined from underground or open-pit mines and can contain as little as 2.5 grams of gold per tonne of ore to as much as 20 grams per tonne.
  3. The cost of extracting gold can vary widely depending on the mining method used and the location of the mine. In general, underground mining is more expensive than open-pit mining.
  4. Cyanide is the most commonly used chemical for gold extraction. It is highly toxic and must be handled with extreme care.
  5. The process of electro-winning can produce high-quality gold with a purity of 99.99%.
  6. The melting point of gold is 1,064 degrees Celsius, and its boiling point is 2,808 degrees Celsius.
  7. Gold is an excellent conductor of electricity and is highly resistant to corrosion.
  8. The largest gold reserves in the world are located in South Africa, followed by Russia and Australia.
  9. In 2020, the global gold production was approximately 3,200 tonnes.
  10. The price of gold can fluctuate widely depending on supply and demand, economic conditions, and geopolitical factors. In August 2021, the price of gold was around $1,800 per ounce.


In conclusion, the extraction and purification of gold in a laboratory setting involves several complex and delicate processes. Each step of the process must be performed with extreme care and precision to ensure the quality and purity of the final product. Despite the challenges involved, the rewards of successfully extracting and purifying gold are immense, making it one of the most sought-after metals in the world.

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