Geometallurgical Diagnosis of Gold Loss in Refractory Quartz-Vein Gold Tailings Using Automated Mineralogy: A Case Study of the Baolun Gold Mine, Hainan Province, China

To enhance gold recovery from tailings of a quartz-vein gold deposit in Hainan, China, this study systematically characterized the chemical composition, mineral composition, and process mineralogical characteristics of gold particles using inductively coupled plasma optical emission spectrometry (ICP-OES), Advanced Mineral Identification and Characterization System (AMICS), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The results show that the tailings have an average gold grade of 0.44 g/t, and the gold occurs predominantly as native gold (average fineness approximately 92%). The gold grains are predominantly fine (89.74% < 10 µm, n = 312), with 92.31% occurring as locked inclusions, predominantly in quartz and chlorite. Particle-size-dependent liberation analysis reveals that gold liberation is strongly size-dependent: 42.31% of the total gold resides in the −5 µm fraction, where grains are almost entirely locked and complete mechanical liberation is technically and economically unattainable. The fine-grain size and insufficient liberation of gold from gangue minerals are the primary causes of gold loss during processing. Additionally, chlorite, as the dominant locking mineral, is prone to overgrinding and likely induces slime coating on gold surfaces, further impairing flotation recovery. A two-pronged optimization strategy is hypothesized: regrinding to a P80 of 20–45 µm combined with dispersants such as sodium silicate or sodium hexametaphosphate. These findings provide a scientific basis for gold recovery from these tailings and for the processing of similar refractory gold tailings.