The Spanish Mountain gold deposit is classified as a sediment-hosted vein (SHV) deposit, as defined by Klipfel (2005).
Gold mineralization occurs as two main types:
• Disseminated within the black, graphitic argillite. This is the most economically significant form. Gold grain size is typically less than 30 µm, and is often, but not always, associated with pyrite. Disseminated gold has also been associated with quartz veins within faults zones in the argillite.
• Within quartz veins in the siltstone/tuff/greywacke sequences. It occurs as free, fine to coarse (visible) gold and can also be associated with sulphides including galena, chalcopyrite and sphalerite. Highest grades have come from coarse gold within quartz veins.
Disseminated gold within the argillite units is by far the most economically important type of mineralization, and occurs in multiple stratigraphic horizons. From drill core, elevated gold content has been noted within fault zones as well as quartz veins within fault zones. However, the influence of fault zones in relation to the gold content of the deposit is not certain.
Examination of 15 representative core samples of disseminated gold in thin section work by Ross (2006) has concluded the following:
• Native gold (electrum) was identified in four samples, and it occurred as inclusions and fracture fill in pyrite, on crystal boundaries between pyrite crystals and in the gangue adjacent to pyrite. It i ........
