Summary of Gold Gravity Separation

1. Gold Gravity Separation Principle

Gold gravity separation refers to the gold extraction and separation process making use of different moving speed and direction of mineral with different particle sizes, traits and proportion under the combined action of gravity, centrifugal force, medium resistance and mechanical resistance.

Gold gravity separation is the oldest gold extraction process. Gold generally occurs in a form of monomeric native gold in alluvial gold mines, and the particle size is generally greater than 16g/t. Therefore, gold gravity separation is one of the most effective and economical processing methods for alluvial gold extraction. However, in general, the single gold gravity separation process is not suitable for vein gold ore extraction and if combined with other gold extraction process, the vein gold separation effect will be better.

2. Gold Gravity Separation Types

（1）Jigging Gold Gravity Separation

Jigging gold gravity separation method is a kind of beneficiation process for gold ore with jigging machine as the main gold gravity separation machine. The jigging machine has some merits including simple structure, large extraction capacity of per unit area, and convenient operation and maintenance. On modern large-scale gold mining vessels, the jigging machine has become the main gold extraction equipment, which can recover monomer gold directly from alluvial gold. The main factors affecting the work of the jig are: stroke and brewing, undersize supplemental water, artificial bed stone and bed thickness, mineral water, feeding amount and screen.

（2）Shaking Table Gold Gravity Separation

Shaking table gold gravity separation is a beneficiation process for gold ore with shaking table as main gold gravity separation equipment. The shaking table is a gravity separation equipment that combines a beveled water flow with a mechanical shaking action. The shaking table consists of three parts: the bed surface, the frame and the conveyor. The bed surface is driven by the transmission mechanism to make longitudinal reciprocating motion. After the slurry is fed to the shaking table, it is subjected to lateral water flow and longitudinal reciprocating shaking on the bed surface. The ore particles achieve mineral layer based on specific gravity and particle size, and moved in different direction of the bed surface, and finally divided into concentrate, middlings and tailings. The effective recovery particle size of the shaking table is 2-0.04mm.

（3）Spiral Chute Gold Gravity Separation

Spiral chute gold gravity separation is a kind of beneficiation process with spiral chute as the main gold gravity separation equipment. As a wooden (or steel) narrow chute with an inclination of 3° to 4° (maximum of 14° to 16°), the spiral chute's separation principle is as follow: after the slurry is fed into the chute from the trough, under the combined action of the force of the water flow, the gravity of the ore (or centrifugal force), the friction between the ore and the bottom of the trough, the minerals of different density complete loosening layer and separation where the minerals with larger at the bottom of the tank becomes concentrate, and those with small density become tailings. The spiral chute belong to intermittent operation. When concentrate at the bottom is deposited to a certain height, feeding will be stopped and concentrate will be sorted out.

(4) Spiral Concentrator Gold Gravity Separation

The spiral concentrator gold gravity separation process is a gold gravity separation process using spiral concentrator as main equipment. This gold gravity separation process is as following: the ore slurry fed from above the chute flows downward along the chute in a spiral shape. During the flow, the ore particles are stratified. Large particles with small density are distributed on the outer edge of the spiral chute, and fine particles with large density are distributed on the inner edge of the spiral chute. The stratified heavy product is discharged by the discharge port of the inner chute bottom by the interceptor, and the light product is discharged by the end of the spiral chute.

(5) Cone Concentrator Gold Gravity Separation

The cone concentrator gold gravity separation process is a gold gravity separation process using cone concentrator as main equipment. The chute of the cone concentrator is fan-shaped, the chute length is about 1 m, the feed end is 125-400 mm wide, and the chute surface is inclined.

The ore slurry is fed from the center of the upper end and distributed through the distribute cone to enter the extraction cone. The ore particles are stratified by density during the flow on the extraction cone, and the light and heavy products are separated by the intercepting port in the end.

3. Gold Gravity Separation Characteristics

(1) Advantages

• Simple process and low investment

• No need to use chemicals, low mineral processing cost, less pollution to the environment.

• In some cases, using gravity separation to pre-concentration, and using flotation or cyanidation to extract the middlings can save the cost.

• Suitable for the extraction of coarse gold.

(2) Disadvantages

If using single gravity separation process to extract gold, the recovery rate of gold would be low. This process needs to be combined with flotation, cyanidation and other processes.