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.
