Gravity separation is a physical process used to separate minerals based on their density differences. It is widely applied in the mining industry to concentrate ores such as gold, tin, tungsten, iron, chromite, and coal. Here’s an overview of the process:
Principles of Gravity Separation
– Works on the principle that heavier (denser) particles settle faster under gravity than lighter particles when suspended in a fluid (water or air).
– The efficiency depends on:
– Particle size (similar-sized particles separate better).
– Density difference between valuable minerals and gangue.
– Fluid medium viscosity.
Common Gravity Separation Techniques
1. Jigging
– Uses pulsating water to stratify particles by density.
– Heavier minerals settle at the bottom, while lighter ones remain on top.
– Used for coal, iron ore, and gold.
2. Shaking Tables
– A sloped table with riffles vibrates laterally, allowing denser particles to move differently than lighter ones.
– Common for fine gold, tin, and tungsten recovery.
3. Spiral Concentrators
– A spiral trough uses centrifugal force and water flow to separate heavy minerals from lighter ones.
– Used for iron ore, chromite, and mineral sands.
4. Centrifugal Concentrators (e.g., Knelson/Falcon Concentrators)
– Uses high-speed rotation to enhance gravitational force for fine particle separation (e.g., gold recovery).
5. Dense Media Separation (DMS)
– Uses a dense liquid (ferrosilicon/magnetite suspension) to float lighter minerals and sink heavier ones.
– Applied in diamond and lead-zinc ore processing.
6. Hydraulic Classifiers & Sluice Boxes
– Water flow separates coarse heavy minerals (e.g., placer gold) from sand/gravel.
Advantages
– Low operational cost (no chemicals needed).
– Environmentally friendly compared to flotation or leaching.
– Effective for coarse and liberated particles.
Limitations
– Less effective for very fine particles (<50 microns).
– Requires significant density differences between minerals.
– May need pre-.jpg)
centration (e.g., screening) for optimal results.
Applications
– Gold placer mining.
– Tin & tungsten ore processing.
– Coal washing.
– Iron ore beneficiation.
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