The cache is just a short 45 minute drive east of Sacramento on
Jackson Highway (Hwy 16) to Highway 49 between the towns of Sutter
Creek and Amador City. The exit to the Sutter Gold Mine is well
marked off of Highway 49. Just look for the iron sculptures of
miners.
The intent of this cache is three-fold. One, you’ll learn how
gold was deposited in this region. Two, you’ll also learn about
local history as well as how important the gold rush was to
California State history and to the Nation’s history. And three, it
is a fun trip to see a working hard-rock gold mine and the kids
will love it! You can visit the Sutter Gold Mine for
more information to plan a trip. Mine tours are available for the
entire family.
The Mine Entrance
Gold is commonly associated with igneous rocks. Igneous rocks are
one of the three great groups of rocks, the other two classes being
sedimentary and metamorphic. Igneous rocks can be classified in two
ways; lava that spills out over the Earth’s surface is called
extrusive; magma that doesn’t reach the surface before it cools and
solidifies is called intrusive. Gold, like other metallic ores, is
concentrated by magmatic processes. The concentrations of minerals
result from differences in crystal structure, density, order of
crystallization, and other factors. Magmatic segregation is a
process in which heavy mineral grains crystallize and sink in fluid
magma forming layers at the base of the igneous rock body. Because
of differences in crystal shapes, rare metals, such as gold, are
separated from the liquid magma as it cools. Gold crystallizes late
in the cooling process. These gold rich solutions are then squeezed
into fractures in the surrounding rock structure where the gold is
precipitated out of the solution as a vein. Quartz is a silicate
mineral that is formed from these solutions of molten rock being
injected into fractured rock. As the quartz vein is formed, the
gold is deposited with it. That’s way gold miners look for quartz.
It is more abundant and within it you might find gold.
Gold in Quartz Matrix
There are two main ways of obtaining the gold from the quartz
veins. The easiest is from placer mining. A placer gold deposit
occurs when a quartz vein is exposed to weathering. The rock
surrounding the quartz is eroded and washed away by hydraulic
processes. The quartz can then be broken down by the same
processes, which frees the gold from the quartz matrix. Since gold
is many times denser than the parent rock or the quartz, it gets
concentrated in stream beds forming a placer deposit. The other way
to obtain the gold is through hard-rock mining. Miners locate the
quartz veins by sample core drilling and then tunneling to the
quartz vein and begin removing it so that it can be processed at
the surface and the gold removed. The processing consists of
physical and chemical means of extraction. At one point in time
miners employed a chemical process called cyanide leaching. The
gold ore was pulverized into a powder and then the gold was
dissolved by sodium cyanide. The solution was then processed
further by chemical means in order to precipitate out the gold,
which could then be smelted to further refine it.
The Sutter Gold Mine is an example of hard rock mining. If you
chose to take the tour into the mine, the extraction process used
here will be explained step by step starting with a lecture and
then a walk along a quartz vein in which you can actually see gold
nuggets still locked in the quartz.
To claim this cache as a find, please take
a photograph of yourself in front of the sign at the posted
coordinates and e-mail me the answer to this question: "What is the
average amount of gold found in one ton of the ore produced
here?"