The mineral processing workflow is a series of steps that transform raw ore into valuable products by extracting the valuable minerals while removing waste materials (gangue). This process can vary based on the type of ore, the desired product, and the specific methods used, but in general, the key steps include:

1. Ore Extraction (Mining)

The first step in the mineral processing workflow involves extracting the ore from the earth. This can be done through either surface mining (open-pit or strip mining) or underground mining (shaft or drift mining), depending on the location and depth of the ore deposit.

  • Drilling and blasting: For hard rock ores, explosives are used to break the rock and expose the minerals.
  • Loading and hauling: The broken ore is then transported to the processing plant.

2. Comminution (Crushing and Grinding)

Once the ore is extracted, it is typically too large to be processed directly. The next step is to break the ore down into smaller particles, making it easier to extract valuable minerals. This process is known as comminution and includes two main stages:

  • Crushing: Large rocks are reduced in size using crushers (e.g., jaw crushers, cone crushers, or impact crushers).
  • Grinding: After crushing, the ore is ground into a finer powder using mills (e.g., ball mills or SAG mills) to further reduce particle size and increase surface area for the next steps in processing.

Goal: The goal of comminution is to liberate the valuable minerals from the surrounding waste rock (gangue).

3. Classification and Screening

After grinding, the material is often classified by size to ensure that only the appropriately sized particles proceed to the next steps. This can be achieved through:

  • Screening: Using screens or sieves to separate particles of different sizes.
  • Cycloning: Using hydrocyclones to separate fine particles from coarser ones based on their density and size.

Goal: To separate the finely ground material from larger, unprocessed rock.

4. Gravity Separation (For Some Ores)

Some minerals, particularly those that are dense or heavy, can be separated using gravity separation techniques. This step utilizes the difference in density between valuable minerals and gangue.

  • Jigging: Using a pulsating water stream to separate materials based on their specific gravity.
  • Shaking tables: A vibrating surface is used to separate particles by gravity.
  • Heavy media separation: The ore is placed in a dense medium (e.g., water with suspended ferrosilicon) where heavier particles sink and lighter ones float.

Goal: To concentrate the valuable minerals by removing lighter, less valuable material.

5. Froth Flotation (For Sulfide Ores)

Froth flotation is a widely used method, especially for ores containing sulfide minerals (e.g., copper, lead, and zinc). It involves adding chemicals (collectors, frothers, and modifiers) to a slurry of ground ore and water. Air is then bubbled through the slurry to create foam, which captures hydrophobic particles (valuable minerals).

  • Mineral collectors: Attach to the surface of valuable minerals to make them hydrophobic (water-repellent).
  • Froth formation: Air bubbles attach to the hydrophobic particles, allowing them to float to the surface where they can be collected.

Goal: To separate valuable minerals from gangue and concentrate the desired minerals in the froth.

6. Magnetic Separation (For Magnetic Ores)

In some cases, minerals can be separated using magnetic separation, particularly when one or more of the target minerals are magnetic (e.g., magnetite or ilmenite).

  • Low-intensity magnetic separators (LIMS): Used for weakly magnetic materials.
  • High-intensity magnetic separators (HIMS): Used for strongly magnetic materials.

Goal: To remove magnetic materials from non-magnetic gangue.

7. Leaching (For Gold and Other Metals)

Leaching is a chemical process used primarily for the extraction of metals such as gold, silver, and copper from their ores. The ore is treated with a solvent that dissolves the metal, allowing it to be separated from the rest of the material.

  • Cyanidation: A process in which gold ore is treated with a cyanide solution, which dissolves the gold.
  • Acid leaching: Used for ores like copper and nickel, where acids (e.g., sulfuric acid) dissolve the metal.

Goal: To chemically dissolve and separate the metal from the ore.

8. Thickening (Concentration)

Thickening involves the removal of excess water from the slurry (which consists of finely ground ore and water) to produce a thickened slurry or concentrate. This step is often done in thickeners or clarifiers.

  • Sedimentation: The heavier particles settle at the bottom, leaving the lighter water to rise to the top.
  • Filtration: In some cases, the slurry is filtered to remove excess water.

Goal: To increase the solid concentration and reduce the volume of water to be treated or disposed of.

9. Dewatering

Dewatering is the process of removing water from the concentrated slurry to obtain a dry concentrate that can be further processed or sold.

  • Centrifugation: Using centrifuges to spin out the remaining water.
  • Vacuum filtration: Using vacuum filters to remove water from the concentrate.

Goal: To produce a dry mineral concentrate ready for shipment or smelting.

10. Smelting and Refining (For Certain Metals)

In some cases, especially for metals like copper, gold, and iron, the final stage of processing involves smelting, where the concentrated mineral is heated to high temperatures in a furnace to extract the metal.

  • Smelting: Involves heating the concentrate with a reducing agent (like coke) to separate the metal from its ore.
  • Refining: Further purification of the metal to remove impurities. This may involve electrolysis, chemical treatment, or other techniques.

Goal: To produce high-purity metal for industrial use.

11. Tailings Disposal and Waste Management

After the valuable minerals are extracted, the remaining material (tailings) must be dealt with properly to prevent environmental damage. This typically involves:

  • Tailings ponds: Large storage facilities for tailings, often requiring careful monitoring to prevent leaks and contamination.
  • Recycling: In some cases, the tailings may be processed further to extract residual minerals or used in other industries (e.g., construction).

Goal: To safely store or dispose of the waste materials without harming the environment.

12. Final Product (Shipping and Marketing)

The final step in the mineral processing workflow is the sale or shipment of the processed product to customers or markets. The product might be:

  • Concentrates: Higher-grade mineral concentrates (e.g., copper, gold, or iron concentrates) that are sold to smelters or refineries.
  • Refined metals: Finished products like pure gold bars or copper cathodes.

Goal: To deliver the processed material to end-users, such as smelters, refineries, or manufacturers.