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schist hosted hydrothermal veins

  • Gold eroded from veins has been concentrated in sediments in valleys, basins and coastal plains as alluvial gold deposits in all gold bearing areas of New Zealand.
  • These alluvial gold deposits have been, and are, an important resource especially in Otago and Southland.
  • see The Gold Cycle (Southern Alps) and Gold at St Bathans

Mercury (Hg) in alluvial gold

  • Alluvial gold in some Southland valleys has recently been found to contain a high mercury content.
  • Mercury sulphide (cinnabar, HgS) from hydrothermal veins (see map) is commonly found with alluvial gold in gravels.
  • Dissolved mercury in streams is elevated above background but is lower than drinking water limits.
  • Miners melting recovered gold have inadvertently inhaled and ingested high levels of mercury.
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