American River at Coloma EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
The American River flows down the western side of the Sierra Nevada mountains, thru Coloma and into Folsom Lake, then Lake Natomas, and enters the Sacramento River at Sacramento. At Coloma one is able to see the historic spot where gold was discovered.
In January of 1848 James Marshall was building a sawmill for John Sutter, a well-known Sacramento businessman. While digging the tailrace for the mill, Marshall spotted nuggets of gold in the gravel. This event led to the greatest mass movement of people in the Western Hemisphere and was the spark that ignited the spectacular growth of the West during the ensuing decades.
Panning for gold and using sluice boxes is known as "placer mining" (as opposed to tunneling into a mountain to find gold in quartz veins, known as "hard-rock mining"). In panning, one places some gravel in a large metal pan, adds water, then agitates the pan. The heavy gold collects in the bottom of the pan, as the overburden washes away over the side. The same principle can be used in a sluice box. The narrow, open-ended box is placed in shallow water, deep enough for the current to flow thru it. The gravel is then shoveled into the box, with the gold being caught in transverse riffles along the bottom of the box. The use of the sluice box allows one to process a lot more alluvial gravel than the use of the time-consuming gold pan.
During the California Gold Rush miners would use giant powerful hoses (called monitors) to wash hillsides down thru a series of sluice boxes. Not only was this process of hydraulic mining destructive to the terrain, the silt from the tailings would clog rivers for many miles downstream. Hydraulic mining was halted by court order in 1884.
It is interesting to speculate where coarse gold comes from. If the magma water is hot enough, the pressure high enough, and the chemistry is right (acids, and other elements like sulfur are present), then gold, quartz and other things you don't expect to see dissolving will go into solution. The solutions move by natural convection (hot things rise), and as they rise the waters cool as they move farther from the heat source in the ground and closer to the surface. The gold is combined with sulfur to form gold-sulfur chemicals that dissolve in the water. At high temperature, gold will react with sulfur and other elements to form soluble chemicals. These chemical complexes are not all that stable, so that when the waters cool and the pressure drops, the chemicals decompose, releasing the gold to form nuggets. Sulfur is very common in geothermal waters (like hydrogen sulfide--the odor of rotten eggs). Most natural hot springs have that sulfur odor quite strong, and most gold-quartz veins have at least some sulfides like pyrite present. Over time, the erosion of veins of gold in higher elevations leads to the gold washing down into the alluvial gravel beds in lower elevations. Such appears to be the case in Coloma.
Parking is available at N 38 48.120 W 120 53.575 for a $5.00 fee. To log this cache, you must post a photo of you (or someone in your party) holding a GPS at the site. E-mail me the answers to the following questions (do NOT post the answers in your log):
1. At N 38 48.100 W 120 53.541, tell me the size of Sutter's Mill and how it was held together. What were the men called who built the nearby cabin?
2. At N 38 48.095 W 120 53.510, tell me how the mill below you operated. Describe the river which is just east of you. Is it laminar (smooth) or turbulent flow? How wide is it? Last, walk to the narrow building about 20 yards south of your position, and describe what is on display inside.
3. Have you ever panned for gold? If so, how is it that the gold stayed in your pan and didn't wash over the side?
Additional Hints
(No hints available.)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures