Which kind of ore is suitable for heap immersion?
The gold leaching method is relatively thick, and the leaching rate of gold is relatively low. Therefore, in general, it is only suitable for treating low-grade gold ore, especially low-grade oxidized ore. Most of this part of the mine is a surface oxide ore.
The large number of industrial practice has proved that for heap leaching of oxide ores, ore occurrence of different types of gold, gold-bearing quartz veins have, BRECCIA, structural alteration, andesite, sandstone, porphyry, heat metamorphic fluid silicide mylonite secondary dozen auriferous iron cap, wherein a high degree of oxidation, occur in small fractures gangue minerals or gold particles easily understood and readily exposed gold heap leaching.
Gold ore having the above characteristics and suitable for heap leaching treatment mainly belongs to the following three types.
1 dip dyed oxidized ore;
2 sulphide ore in which gold is not symbiotic with sulphide minerals;
3 A vein gold or gold deposit containing a small gold particle or a gold particle with a large specific surface area.
Ore suitable for gold extraction by heap leaching shall have the following characteristics:
1 Gold grade is low, most of them are in the range of 1.0~3.0g/t, and the gold ore grade of only some deposits is greater than 3.0g/t;
2 gold inlaid fine grain size, or flat type, easy to cyanide leaching;
3 ore is loose and porous due to oxidation and weathering, and is permeable;
4 using the crushing method to expose the gold in the ore with few pores;
5 ore contains no or little acid, and contains no or little element which can react with cyanide;
The 6 ore contains no substances that adsorb or precipitate dissolved gold.
The table below lists the types and properties of gold ore that have proven to be suitable for gold extraction by heap leaching.
Heap leaching ore type and nature | ||||||
Serial number | Deposit or ore type | Gold particle size | Relationship between gold and carrier minerals | Harmful element content | Ore permeability | Ore appearance |
1 | Quartz vein oxidized ore | Medium grain, fine grain | Gold is mostly produced in limonite | Rarely | good | Gold-bearing sulphide ore is oxidized to limonite, weathering is severe, and crack development |
2 | Porphyry | Fine grain | Mainly in quartz, feldspar , limonite | Very few | good | The degree of oxidation is high, the weathering is serious, the cracks develop, and the secondary pores are densely packed. |
3 | Altered andesite | Fine grain | Natural gold 50% in mineral cracks | Rarely | good | Cracks and voids in the ore, good permeability |
4 | Carbonate type | Fine | Mainly in calcite , followed by quartz | Very few | good | The good ore is crushed and crushed, and the secondary pores are network-like and highly oxidizing. |
5 | Tectonic altered rock | Fine | Coexisting with limonite and cuttings | Very few | good | Extrusion, crushing, loose texture, crack development, many holes |
6 | Gold-bearing iron cap | Fine grain | Gold is produced in limonite and quartz. | More copper | general | The degree of oxidation is deep, the cracks develop, and the ore is muddy. |
7 | Metamorphic hydrothermal type | Fine grain | Major quartz, followed by limonite | Silver higher | general | Strong weathering, serious muddy, dense secondary holes, high degree of oxidation |
8 | Silicified mylonite | Fine | In limonite, jarosite, quartz | Very few | general | Severe muddy, deep oxidation, secondary pores such as cobwebs |
9 | Sandstone type | Fine grain | Gold is produced in quartz sandstone | High copper | good | The degree of oxidation is general and the structure is dense |
10 | Hydrothermal filling type | Fine grain | Produced in limonite and peptizer | Lead Zinc High | general | Strong weathering, serious ore mud, cracks, and dense holes |
11 | Broken breccia | Fine | In quartz, limonite and peptizer | Slightly higher sulfur | good | The degree of oxidation is general, the pores are cracked, and there are many cemented materials. |
12 | Altered basalt | Fine | Gold particles are mostly in fine mud | Very few | general | The ore contains a high amount of mud, which requires a heap leaching of the ore. |
13 | Muddy siltstone | Very fine | Gold particles are often found in fine mud | Very few | general | The ore contains more than 30% of mud, such as agglomeration treatment, the leaching rate can reach 80% |
14 | Silicified altered rock | Fine | Dip-like, distributed in altered rock | Very few | good | The ore is highly oxidized, the fractured pores are developed, and the leaching is easy. |
The three important physical properties of the heap leaching ore are: 1 fine fraction; 2 saturated water capacity; 3 loose density, ie bulk density.
The fine fraction content in the ore generally refers to a material of less than 74 μm or less than 149 μm, which has a great influence on the permeability of the ore heap leaching: high fine fraction and low permeability. Generally less than 74 μm, when the content exceeds 5%, granulation heap leaching is required.
The ore saturated water-capacity rate refers to the percentage of the ore's water content to the total mass of the ore after being saturated with water (dry mine weight plus water absorption) when the ore water reaches saturation state. It is another important factor affecting the permeability of ore. This value is not only related to the grain size of the ore, but also to the mineral composition of the ore. Kaolin, chlorite, sericite, etc. have a strong water-absorbing mineral ores contained. When a solution passes between the ore particles, these minerals absorb a large amount of water and swell, causing the original high-strength ore particles to be broken, even pulverized and muddy, thereby significantly deteriorating the permeability of the ore.
The loose density of ore, this value is directly related to the relationship between the volume of the ore and the quality of the ore. Therefore, it is also a more important parameter in heap leaching.
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