The Ancient River of Gold

The Ancient Rivers of Gold in northern California are from the Tertiary Period. The Tertiary rivers existed millions of years ago and many of them had large quantities of gold within their gravels. Because of that, they are known as the "Ancient Rivers of Gold."

These now-dry Tertiary rivers are thought to be a prime source of the gold found in many of the rivers and streams of the Mother Lode region of northern California. The ancient rivers are discontinuous and sometimes follow tortuous routes. They have been altered by volcanic activity, erosion, and in some instances portions of the rivers have been covered by lava. Much of the region underwent extreme volcanic eruptions. Volcanic flows have been found up to 4,000 feet deep. Volcanic flows were up to 60 miles in length. Portions of an ancient river may be found at ground level or near the top of a mountain, or on the side of a mountain, or buried.

Early prospectors found portions of the ancient rivers and worked them for their rich gold content. Later, mining companies used hydraulic mining or drift mining techniques to recover the gold. In hydraulic mining, water under pressure is directed to, for example, the side of a ravine to dislodge the gravels and send the material to the sluices where the gold is recovered. The equipment that was used (called a "monitor" or "giant") was similar to a very large hose nozzle.

Geologic reports speak of gravel deposits up to 250 feet deep with gold deposits interspersed at various levels within the gravels. Some of the gravels of the ancient rivers of gold have been cemented together over time. Smaller materials between the larger gravels have bound the larger gravels together. Drift mining is used in those instances to follow the channel underneath the volcanic covering. In drift mining, tunnels are driven in bedrock underneath the channels and when the channels are reached, the richest stratum, resting immediately on the bedrock, is extracted by underground mining methods and then washed at the mouth of the tunnel.

Many miles of the ancient rivers are still un-worked and may be very rich in gold.