Heap leaching is used to extract gold. Because the ore particle size is relatively coarse and the reaction with cyanide leaching agent is weak, the leaching rate of gold is relatively low. Therefore, it is generally only suitable for processing low-grade gold ores, especially low-grade oxidized ores, and most of these ores are surface oxidized ores.

According to a large number of industrial practices, among the oxidized ores available for heap leaching, the types of ores in which gold is stored are different, including gold-bearing quartz veins, gold-bearing breccias, tectonic altered rocks, andesites, sandstones, porphyry, hydrothermal metamorphic rocks, silicified mylonites, and secondary gold-bearing iron caps. Among them, gold with a high degree of oxidation, gold in gangue or mineral fissures, and gold with small particles and easy to be exposed are easy to heap leaching.

Gold ores with the above characteristics and suitable for heap leaching mainly belong to the following three types:

① Disseminated oxide ore;

② Sulfide ore where gold is not closely associated with sulfide minerals;

③ Vein gold ores or placer gold ores containing tiny gold particles or gold particles with large specific surface area.

Ores suitable for heap leaching should have the following characteristics:

① Low gold grade, most of which are in the range of 1.0~3.0g/t, and only individual deposits have a gold ore grade greater than 3.0g/t;

② The gold is finely embedded or flat, which is easy to cyanide leached;

③ The ore is loose and porous due to oxidation and weathering, and has permeability;

④ The crushing method can expose the gold in the ore with very few pores;

⑤ The ore contains no or little acidic substances, and no or little elements that can react with cyanide;

⑥ The ore does not contain substances that adsorb or precipitate dissolved gold.

The three important physical properties of heap leaching ore are:

① fine particle content;

② saturated water capacity;

③ loose density, i.e. bulk density.

The fine particle content in the ore generally refers to materials less than 74μm or less than 149μm, which has a great influence on the permeability of the ore heap leaching: the fine particle content is high, the permeability is reduced. Generally less than 74μm, when the content exceeds 5%, granulation heap leaching is required.

The saturated water capacity of the ore refers to the percentage of the water content of the ore to the total mass of the ore saturated with water (dry ore weight plus water absorption) when the ore absorbs water to saturation. It is another important factor affecting the permeability of the ore. This value is not only related to the particle size of the ore, but also more closely related to the mineral composition of the ore. Minerals such as kaolin, chlorite, and sericite contained in the ore have strong water absorption. When solution passes between mineral particles, these minerals absorb a large amount of water and expand, causing the original high-strength mineral particles to break, even pulverize and muddy, thereby significantly deteriorating the permeability of the ore.

The loose density of the ore is directly related to the relationship between the volume of the ore pile and the quality of the ore. Therefore, it is also a more important parameter in heap leaching.