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Alluvial mining of gold

An overview of an example of a gold mining operation supplied by airplane. See how small gold particles can be recovered.

This operation was supplied by air, so an airstrip, a camp, all mining equipments, etc.. had to be constructed on site. The forest clearing was done by hand.

The operation produced over 70,000 ozs. ( 2,177 kg.) in three years.

Average overall gold grade was: 0.456 g/m3.
Cutoff grade was: 0.1 g/m3 at a price of 350 US $/ oz..

Reserves, estimated by exploration, were 5% less than the actual production.
Exploration involved sampling of a total vertical section ( 12 to 17 m. deep). Very fine particles of gold were distributed from the top to the bottom.
Many alluvial diamonds were found, but the recovery was optimized for gold. The rate of mining was over 5,000 m3 per day.

Gold particles size distribution in this gold placer deposit:
 % of particles in MESH size groups for:

Gold particle size distribution

  • a/."Banka" drill sample
  • b/. Sample from a sluice box (top riffles row #1)
  • c/. Sample from a sluice box (top riffles row #2)
  • d/. Sample from a sluice box (the carpet covered by frames, see the image below.)
Sluice box

After changing last 5 rows for carpets covered by especially designed frames, out of 8 rows in total, the average gold recovery was increased by 62%.


Rafal Swiecki, geological engineer email contact
Feb, 2006
This document is in the public domain.


Seismic Survey