Placer mining is a kind of surface, open-pit mining. Many times water erosion separated the metals from the rocks... wearing it away until the metal flakes, nuggets, and dust flowed with the water into nearby streams and rivers. As the flow of water slowed, the metals would drop to the bottom and lodge in the sand and silt.
Placer mining was done in rivers, creeks, and streams. Simply said, the miner scooped dirt into a pan from the bottom of a stream, river, or creek. He swirled the dirt and water and then poured the water out of the pan [panning]. Since gold was heavier, it would be left in the pan.
If there were lots of gold nuggets, a rocker was used. Rockers were long boxes into which dirt and water were shoveled . The box would be rocked combining the water and dirt, and this poured out the end of the box leaving the gold behind. Sluices were used as a more effective method.



Open-pit mining, also known as opencast mining and open-cut mining and strip mining, refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow.

The term is used to differentiate this form of mining from extractive methods that require tunneling into the earth. Open-pit mines are used when deposits of commercially useful minerals or rock are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling (as would be the case for sand, cinder, and gravel). For minerals that occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock— underground mining methods extract the valued material.

Open-pit mines that produce building materials are commonly referred to as quarries.


Accessing underground ore can be achieved via a decline (ramp),incline vertical shaft or adit.
Declines can be a spiral tunnel which circles either the flank of the deposit or circles around the deposit. The decline begins with a box cut, which is the portal to the surface. Depending on the amount of overburden and quality of bedrock, a galvanized steel culvert may be required for safety purposes. They may also be started into the wall of an open cut mine.
Shafts are vertical excavations sunk adjacent to an ore body. Shafts are sunk for ore bodies where haulage to surface via truck is not economical. Shaft haulage is more economical than truck haulage at depth, and a mine may have both a decline and a ramp.
Adits are horizontal excavations into the side of a hill or mountain. They are used for horizontal or near-horizontal ore bodies where there is no need for a ramp or shaft.
Declines are often started from the side of the high wall of an open cut mine when the ore body is of a payable grade sufficient to support an underground mining operation but the strip ratio has become too great to support open cast extraction methods.

Ore Access
Levels are excavated horizontally off the decline or shaft to access the ore body. Stopes are then excavated perpendicular (or near perpendicular) to the level into the ore.

Ventilation
Door for directing ventilation in an old lead mine. The ore hopper at the front is not part of the ventilation. One of the most important aspects of underground hard rock mining is ventilation. Ventilation is required to clear toxic fumes required for cooling the workplace for miners. Ventilation raises are excavated to provide ventilation for the workplaces, and can be modified to be used as escape routes in case of emergency.