VOLUME 19 (Supplement)

Characterization of tailings and low-grade ore from small-scale gold mining (SSGM) in Paracale, Camarines Norte and from large-scale gold mining (LSGM) in Aroroy, Masbate: Assessing environmental risks and sustainability for future green lixiviant applications

This study characterizes the geochemistry and mineralogy of low-grade ore, muck-outs and tailings from a small-scale gold mining (SSGM) site in Paracale, Camarines Norte, and a large-scale gold mining (LSGM) operation in Aroroy, Masbate, to identify possible environmental hazards and resource-recovery potential. Samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), direct mercury analysis, fire assay, X-ray diffraction (XRD), reflected-light petrography, automated scanning electron microscopy (Zeiss Mineralogic), and sieve-hydrometer grain-size analysis. The two sites differ in composition and mineralogy. Paracale tailings (n = 4) retain precious and base metals, with medians of 8.64 g/t Au (range: 12.56), 46.48 g/t Ag (range: 341.54), and 0.45% Cu (range: 1.14), in a siliceous matrix (71.30-79.92% SiO₂). Paracale tailings contain liberated electrum, refractory tellurides, and mercury-bearing Au-Ag amalgam particles, with accessory uraninite and monazite in the fine (< 63 µm) fraction examined. In contrast, Masbate tailings (n = 3) contain medians of 0.20 g/t Au (range: 0.08) and 0.74 g/t Ag (range: 0.12) in an aluminosilicate matrix with calcium oxide (2.58-4.52% CaO). Gold occurs within sulfides, mainly arsenian pyrite, and rare-earth-element phosphates are also present. Paracale tailings contain high concentrations of potentially toxic elements, including medians of 35.05 mg/kg total mercury (THg; range: 96.71), 5,000.00 mg/kg Pb (range: 4,751.90), and 1,876.45 mg/kg As (range: 6,609.40). Masbate shows localized arsenic enrichment, with medians of 128.60 mg/kg As (range: 44.20) in tailings and 483.80 mg/kg As (range: 903.20) in low-grade ore. These results provide a comparative baseline for the sampled materials; broader spatial sampling is needed for any regional assessment. Paracale tailings may be a candidate for secondary metal recovery and targeted remediation, whereas Masbate's arsenic-bearing wastes may require groundwater monitoring and containment. These contrasting profiles provide a basis for later evaluation of technologies such as green lixiviants for tailings management and resource recovery.