The Mine’s surface and mineral rights are owned by Minerales de Occidente, S.A. de C.V. (Minosa), a wholly-owned indirect subsidiary of Aura existing under the laws of Honduras.
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Summary:
Deposit Types
The San Andrés deposit as an epithermal gold deposit associated with extensional structures within tectonic rift settings. These deposits commonly contain gold and silver mineralization, which is associated with banded quartz veins. At San Andrés, silver is not economically important. Gold occurs in quartz veins that are predominantly comprised of colloform banded quartz, generally chalcedony, with lesser amounts of fine comb quartz, adularia, dark carbonate, and sulphide material. The gold mineralization is deposited as a result of cooling and the interaction of hydrothermal fluids with groundwater and the host rocks. The hydrothermal fluids may have migrated some distance from the source; however, there is no clear evidence at San Andrés that the fluids, or portions of the fluids, have been derived from magmatic intrusions. Many of these low sulphidation epithermal deposits occur in felsic volcanic sequences where geothermal fluids are circulating. Near surface, many deposits are capped by eruption breccias which are formed by the rapid expansion of depressurized geothermal fluids. These breccias are characterized by intensely silicified matrix and angular fragments of the host rock. Wall rock alteration forms as halos to veins and includes sericite grading to peripheral smectite and marginal chlorite alteration.
Corbett (2002) suggests that structure and the competency of the host rocks may be important ore controls for the vein systems. The extension fractures form in the stronger, more competent rocks. Higher grade ore shoots generally develop in areas with a greater frequency of extensional structures, or at dilational jogs or flexures in the veins. The mineralization at San Andrés appears to be in an upper level epithermal system as indicated by the hydrothermal alteration patterns, the disseminated style of mineralization, the presence of both gold and silver associated with quartz veining, the presence of active hydrothermal fluid flow at the property, and the actively forming extensional fracture system, which creates the permeability.
Mineralization
At the Mine, gold and silver mineralization is associated with a high level epithermal, quartzcarbonate-adularia system consisting of veins, stockworks, and disseminations. In the andesite, overlying conglomerate and rhyodacite, the quartz veins are typically composed of banded chalcedony and fine-grained white quartz, which has replaced calcite. The bladed calcite texture seen in veining is ubiquitous and the quartz replacement is almost always complete. Metallurgical studies show that the gold is primarily contained in electrum as fine-grained particles. The particle size of the electrum grains varied from 1 µm x 1 µm up to 10 µm x 133 µm. One native gold grain was noted.
Sulphur mineralization in the Mine is not considered as Mineral Resources or Mineral Reserves as there are no current or planned recovery methods for sulphur mineralization.
SLR assessed the ratio between the silver assays that were available with the gold assays in the 2024 Reserve and Resource pit at a 0.187 g/t Au cut-off. The ratio was 4 to 1, However, because of the much lower price for silver and the lower metal recoveries, the value of the silver recovered is less than 1 to 2% of the value of the gold produced. Therefore, samples are not generally analyzed for silver and silver grades are not included in the block model.