Alluvial Gold and Its Recovery

Schools - Successful South Coast Panning
Gold Equipment - Wooden Rocking Cradle


Alluvial gold in the Mogo area was discovered in the old waterways and drainage systems and formed the basis upon which the gold-rush was founded.

Formation  And Degradation Of Gold Bearing Quartz Reefs

After the earth was formed, cracks appeared in the rock as a result of several influences (temperature variations and contraction of the planet's surface). These cracks, or shears, caused a pressure release allowing quartz, in solution, to well up. Gold, silver and other elements entered into these shears with the quartz.

It is believed that after the forming of the quartz reefs, the planet experienced periods of intense cold (the ice ages) and periods when, it is believed, the annual rainfall may have been up to 1000 inches a year. This caused massive amounts of erosion over a long period of time and the Mogo we know may well have been 100s of metres under the original surface of the earth.

As the drainage systems formed during this period of erosion, the gold, liberated from the reefs, was washed down together with all the other rock matter. These drainage systems acted like giant sluices, by collecting the gold in all the cracks and crevices on the rocky bottoms of the waterways.

Over the passage of time and up to the modern day, the earth has gradually changed and the old waterways have been, in places, completely buried, or partially covered, leaving only narrow creek beds. In the Mogo area these narrowed waterways were where the alluvial gold was found by the diggers.

Easy Pickings

The gold that was easily found and panned, was the catalyst that brought the diggers to the Araluen fields. As the easily available gold was taken, the banks of the creeks were mined to expose the rest of the old drainage systems.

The alluvial gold was, of course, fully liberated but buried in the silts, clays and light shales. These had to be separated. There was a variety of methods employed to achieve this, the most common of these being the sluice and the cradle. Both of these methods involved shovelling the alluvial ore onto the machine and dispersing the clays, etc. with water. The last small separation was achieved by panning.

Tinning

When diggers collected the gold that was too fine to pan, they would use a method called "tinning". This involved rubbing mercury in their pans to trap the gold (These two elements have a chemical affinity and are attracted to each other). The digger then placed his pan in the fire to "melt" the resulting amalgam, which would then be placed in a hollowed out potato, wired together and thrown in the fire. The spud would then be cooked until it was black on the outside. At this point the mercury was absorbed by the potato, leaving the pure gold inside.

Further Reading
Related Information: