Sepro’s complete understanding of mineral processing allows us to push the limits of our industry. Through decades of research and trials, we’ve engineered powerful, high G-force gravity concentrators and customizable gravity recovery circuits, which deliver unparalleled performance to our customers. But all of our designs, equipment, and processes stem from a thorough understanding of mineral processing fundamentals.
If you have just started learning about our industry or simply need a refresher on the basics of mineral processing, we’ve got you covered. Make sure to check out our quick reference glossary at the bottom of the page to understand some highly used industry terms!
What Is Mineral Processing?
In simple terms, mineral processing is separating commercially valuable minerals or metals from other rocks.
It’s not often that you dig up a large gold nugget. Instead, small particles of gold can be found mixed in with other minerals, metals, and rocks, some valuable, and some not. The collection of all these materials together is called ore. Extracting particles of gold and other valuable material from ore is done by exploiting differences between the materials.
There are a number of ways we can exploit these differences, but before this happens, the ore needs to be crushed.
The process of crushing and grinding ore is called comminution. There are a variety of crushers on the market today like cone crushers, jaw crushers, and grinding mills that pulverize the rock into similarly sized fragments. The grinding and crushing process liberates or “frees” the valuable material for effective recovery to take place in the next steps.
Comminution is the most energy-intensive stage in mineral processing. To make this step more energy efficient, Sepro is working with a team of researchers to develop a system that uses powerful bursts of microwaves to help sort the valuable minerals from waste prior to grinding. The process also creates microfractures in the ore, requiring less energy for future grinding.
Once the ore has been crushed, mineral recovery can take place. Different methods of mineral recovery are employed depending on the type of material to be recovered. We’ll briefly touch on some of the most common processes below. Make sure to read our technical papers for a more advanced take on mineral recoveries.
Size and Hardness
Since some minerals are harder than others or have larger/smaller mineral grains, they respond differently during the comminution process. The different minerals can often be separated by particle sizing using either a screen or hydrocyclone after the crushing process. Understanding the Mohs scale of hardness and mineral grindability will give you an idea of how strong a mineral is.
Occasionally minerals in ore will have a significant difference in colour that allows them to be separated visually.
In general, valuable minerals are denser than barren rocks. We can exploit the different densities of minerals by using the science of gravity separation wherein elements settle at different rates.
By suspending crushed ore in a medium like air or water, heavier particles will settle first and lighter ones on top. The valuable particles become concentrated and can be collected. Gravity separation equipment like the Falcon Gravity Concentrator or the Condor Dense Medium Separator uses this strategy to effectively recover valuable particles.
Some minerals have strong magnetic properties which can easily be exploited for separation. Ferrous metals are magnetic and can be recovered using an electromagnetic separation device. This process is primarily used to recover iron ore.
Metals and minerals in an ore may react differently to certain chemicals. For example, a common gold recovery technique is cyanide leaching. In this process, cyanide dissolves gold in an ore while leaving the barren rock intact. The dissolved gold solution can be re-concentrated using activated carbon, direct electrowinning, or the Merrill-Crowe process.
Choosing The Correct Mineral Recovery Process
The mineral processing concepts described above are quite simple to understand. However, choosing the ideal recovery process (or combination of processes) is the real challenge for optimal recovery. Sepro’s experience and knowledge of mineral systems allow our customers to thrive, regardless of market conditions. If you want a system that consistently hits your target recovery rates, contact our mineral processing experts today.
Quick Reference Glossary
Adsorption: The process by which a solid holds molecules of a gas, liquid, or solute as a thin film.
Assay: The testing of a metal or ore to determine its constituents and quality.
Comminution: The process of crushing and grinding ore into smaller fragments.
Concentrate: The valuable material resulting from mineral processing.
Electrowinning: A metal refining technique that uses electricity.
Fines: Very small particles. Finely ground or crushed ore.
Froth Flotation: A process which selectively separates hydrophobic materials from hydrophilic ones.
Gangue: Waste materials found in ore.
Grade: The percentage of metal in a product.
Gravity Concentrator: Mineral processing equipment that uses high G-forces to separate and recover valuable particles (eg. the Falcon SB Gravity Concentrator).
Gravity Separation: The process of separating different minerals and metals based on their specific gravity.
Leaching: Extracting certain materials from a carrier into a liquid.
Metal: A solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity.
Micron: A unit of length equal to one-millionth of a meter.
Middlings: A mixture of partly liberated particles.
Mineral: In geology, a mineral is a substance that meets five specific requirements. It must be naturally occurring, inorganic, solid, have a definite chemical composition, and have an ordered internal structure.
Mineral Processing: The process of separating commercially valuable minerals from their ores.
Ore: A naturally occurring solid material from which a metal or valuable mineral can be profitably extracted.
Slimes: Very fine particles, often undesirable.
Slurry: A mixture of water and ore particles.
Smelting: The process of extracting metals from their ore by heating and melting.
Tailings: The residue of an ore. This is the leftover material from mineral processing.