How Gold Is Mined, Extracted, and Refined

Gold has been one of humanity’s most valuable and admired metals for thousands of years. Its beauty, rarity, and resistance to corrosion have made it a universal symbol of wealth and security. But before gold becomes the bars, coins, and jewellery we recognise today, it must go through a long, technical, and highly controlled production process.
This article provides a complete and SEO-friendly explanation of how gold is mined, extracted from ore, refined, and transformed into investment-grade bullion.

1. How Gold Forms in Nature

Gold is a naturally occurring precious metal that forms deep within the Earth’s crust. Most gold deposits originate from hydrothermal activity, where hot mineral-rich fluids move through cracks in rocks and deposit microscopic particles of gold over millions of years.
Depending on geological conditions, gold may appear as:

  • Fine particles dispersed in rock
  • Veins inside quartz
  • Gold mixed with sulfide minerals
  • Nuggets and flakes in riverbeds (placer gold)

Although gold is globally admired, it is extremely rare. On average, one tonne of rock contains only 1–10 grams of gold.

2. Gold Exploration – Finding Economic Gold Deposits

Before mining begins, companies must identify where economically viable gold deposits exist. This phase is known as exploration, which includes:

  • Geological surveys
  • Satellite imaging
  • Soil and rock sampling
  • Drilling exploration holes
  • Laboratory mineral analysis
  • 3D mapping of the deposit

If data confirms that a deposit contains enough gold to justify investment, the project moves into mine development.

3. Types of Gold Mines: Open-Pit vs Underground

Gold can be mined using two main methods:

A. Open-Pit Gold Mining

Open-pit mining is used when the gold deposit is located near the surface. Large excavators remove thousands of tonnes of rock daily. Advantages include:

  • High production rates
  • Efficient use of heavy machinery
  • Suitable for low-grade ore

B. Underground Gold Mining

Underground mining is used for deeper deposits. Workers and machines enter the mine through tunnels and shafts. This method is more complex but ideal for high-grade ore bodies deep beneath the surface.

4. Crushing and Grinding – Preparing the Ore

Once the ore is extracted, it must be broken down to release gold particles trapped within the rock. This process includes:

  • Primary crushing
  • Secondary crushing
  • Grinding in large mills
  • Reducing particles to below 1 mm

The goal is to produce a fine slurry where gold can be chemically separated from waste material.

5. Gold Extraction Methods – How Gold Is Separated from Ore

To extract gold from crushed ore, mining companies use advanced processing technologies. The three primary methods are:

1) Cyanide Leaching (CIL / CIP)

This is the most widely used extraction technique worldwide. Gold dissolves into a cyanide solution, forming a stable gold-cyanide complex. Activated carbon is then used to absorb the dissolved gold in either:

  • CIL (Carbon-in-Leach)
  • CIP (Carbon-in-Pulp)

After absorption, gold is stripped from the carbon and recovered.

2) Gravity Separation

Used for ores containing “free gold” (larger particles). Equipment includes:

  • Shaking tables
  • Centrifuges (Knelson, Falcon)
  • Spirals

This technique uses gold’s high density to separate it from lighter minerals.

3) Flotation

Used for gold associated with sulfide minerals like pyrite and chalcopyrite.
The process creates a gold-rich concentrate that is later treated through roasting, pressure oxidation, or direct leaching.

6. Electrowinning – Recovering Gold from Solution

In the next step, gold dissolved in the cyanide solution is recovered through electrowinning, where electrical currents cause gold to deposit onto steel cathodes. The resulting material, known as gold sludge, is dried and prepared for smelting.

7. Smelting – Turning Gold Sludge into Bars

Gold sludge is heated to temperatures between 1,150–1,250°C. Impurities form a molten layer called slag, which is removed.
The molten gold is poured into moulds to produce:

  • Cast gold bars (with natural texture)
  • Dore bars (containing gold + silver + small impurities)

These bars typically contain 85–95% gold and must go through additional refining.

8. Refining – Producing 99.99% Pure Gold

To meet international investment standards, gold must be refined to 99.99% purity or higher.

Two major refining processes are used:

A. Miller Process (99.5% purity)

Chlorine gas is injected into molten gold, causing impurities to bond and float to the surface as slag.

B. Wohlwill Process (99.99–99.999% purity)

An advanced electrochemical process that produces the highest purity gold available.
This is the standard used by major refiners supplying LBMA-approved bullion.

9. Minting or Casting – Turning Pure Gold into Final Products

Once refined, pure gold is transformed into investment products:

Cast Bars (Traditional)

  • Gold is melted and poured directly into moulds
  • Slightly natural and uneven surface
  • Preferred for investors who value low premiums

Minted Bars (High-Precision)

  • Gold is rolled into thin plates
  • Cut into exact dimensions
  • Laser-engraved and sealed
  • Premium appearance with sharp edges

Gold Coins

Refineries strike coins using high-pressure presses, producing:

  • Sovereign
  • Britannia
  • Krugerrand
  • Maple Leaf
  • Kangaroo
  • Philharmonic

Each coin includes a guaranteed weight and purity.

10. Quality Control and Certification

Before leaving the refinery, gold products undergo:

  • XRF metal analysis
  • ICP laboratory verification
  • Precision weighing
  • Serial number registration
  • Packaging and sealing

Investment-grade products usually comply with LBMA Good Delivery standards, ensuring global recognition.

11. Global Distribution and Market Availability

Once certified, gold bars and coins are shipped to:

  • Bullion dealers
  • Banks
  • Investment platforms
  • Jewellery manufacturers
  • International wholesalers

From here، gold becomes accessible to investors and collectors worldwide.

Conclusion – From Earth to Investment Gold

The journey of gold—from deep underground deposits to beautifully refined bullion—is long, technical, and highly controlled. Every gram of gold requires significant exploration, mining, processing, refining, and quality assurance.
Understanding this process highlights why gold remains one of the world’s most trusted and valuable assets, sought after for investment, wealth preservation, and long-term security.