Categories of associated gold and silver minerals

Associated gold is widely present in copper ores, followed by lead-zinc ores, with minor occurrences in molybdenum, platinum, nickel, tin, and tungsten ores. Some iron ores and pyrite also contain associated gold. The primary host minerals include pyrite, chalcopyrite, magnetite, galena, sphalerite, chalcocite, and arsenopyrite. The occurrence state of associated gold within minerals, based on its embedding relationship, can be categorised as: fissure gold, intergranular (intercrystalline) gold, surface-adsorbed gold, encapsulated gold, and lattice gold. The separation processes and difficulty levels for extracting gold vary significantly depending on its embedding state. Depending on the associated minerals, associated gold and silver deposits can be classified into the following categories:

(1) Sulphide gold-silver ores

These ores can be further subdivided based on sulphide content into low-sulphide gold-silver ores and high-sulphide gold-silver ores. As the names imply, in low-sulphide gold-silver ores, gold and silver are the primary recoverable components, with native gold particles being relatively coarse. Other minerals, being present in low concentrations, are either not recovered or only recovered as by-products.

Rich sulphide gold-silver ores contrast with poor sulphide ores, exhibiting lower gold and silver grades. Pyrites and arsenopyrite constitute the primary constituents, present in higher concentrations. Native gold particles are relatively small, occurring as enclosed gold or intergranular gold, with a fine grain size. During separation, it is common to obtain a mixed product of gold/silver with pyrite and arsenopyrite, making the separation of gold/silver from sulphides relatively difficult. Typically, a combined beneficiation and smelting process is required to achieve high beneficiation indices.

(2) Polymetallic sulphide gold-silver ores

These ores contain multiple metallic minerals such as copper, lead, zinc, tungsten, and antimony. Gold and silver are uniformly distributed, with relatively coarse native gold grains. Ore properties may alter during mining, increasing separation complexity and necessitating combined beneficiation-smelting processes. Although sulphide content in such ores is relatively high (10%–20%), they may still be developed as distinct gold-silver deposits. The sulphur and co-occurring metals (copper, lead, zinc) also possess significant recovery value.

(3) Polymetallic sulphide ores containing gold and silver

Depending on the predominant sulphide mineral, these ores may be categorised as: associated with pure copper deposits; associated with copper-sulphide deposits; associated with copper-iron deposits; associated with lead-zinc deposits; associated with copper-zinc deposits; or associated with copper-lead-zinc deposits. Gold exhibits affinity for copper, iron, and sulphur, and the combination of native gold with chalcopyrite is widely encountered in nature.