Mining Gold

In lode or vein deposits, the gold is mixed with another mineral, often quartz, in a vein that has filled a split in the surrounding rocks. Gold is obtained from lode deposits by drilling, blasting, or shoveling the surrounding rock.
Lode deposits often run deep underground. To mine underground, miners dig shafts into the ground along the vein. Using picks and small explosives, they then remove the gold ore from the surrounding rock. The gold ore is then gathered up and taken to a mill for refinement.

Placer deposits contain large pieces of gold ore (nuggets) and grains of gold that have been washed downstream from a lode deposit and that are usually mixed with sand or gravel. The three main methods used to mine placer deposits are hydraulic mining, dredging, and power shoveling. All methods of placer deposit mining use gravity as the basic sorting force.
In the first method, a machine called a "hydraulic giant" uses a high pressure stream of water to knock the gold ore off of banks containing the ore. The gold ore is then washed down into sluices or troughs that have grooves to catch the gold.

Dredging and power shoveling involve the same techniques but work with different size buckets or shovels. In dredging, buckets on a conveyor line scoop sand, gravel, and gold ore from the bottom of streams. In power shoveling, huge machines act like shovels and scoop up large quantities of gold-bearing sand and gravel from stream beds.

Hydraulic mining and dredging are outlawed in many countries because they are environmentally destructive to both land and streams.