This mine was arguably the most productive mine of the gold rush era. It was open for 100 years . Much of the earth is hard granite rock that had to be drilled, as the miners pursued the veins of gold. In fact, there is a 5 mile chunk of rock beneath the surface that the miners drilled into, following the veins, digging more than 300 miles, a labyrinth of tunnels beneath the surface of Grass Valley. The mining technique here was hard rock mining, as they literally bore holes through the rocky earth.
Most other mining techniques involved searching where gold would settle, as it is very heavy. Hydraulic mining involved blasting off hilltops with water cannons and then processing the mud and extracting the gold. Placer mining involved looking for deposits in sand or gravel, in stream beds, in lower areas, where the water flow would deposit the gold nuggets.
If you do TDE1, the whereigo, you will see many of the machines that were developed and are now preserved in the yard.
Here are some images from the visitors center.
Deep beneath Grass Valley.
The Geology: Earth's surface is never stationary. Uplift and erosive processes continually alter landforms. Such large-scale changes may not be apparent in a human lifetime, but they slowly continue to sculpt the earth.
The records are in the rocks.
This hike will take you on a 4 stage hike. Each stage will have one question. You will be studying the rocks, or slag that have been removed from the mines. You will be walking a loop of about 2-3 miles. The 5th stage will be fairly close to the beginning and you can continue down the trail, next to the road to the starting parking lot.
Stage 1: (the listed coordinates). After parking you will want to walk down the main trail until you see the pile of rocks on the left, opposite Stacy Lane trailhead. Wander around a bit and examine a couple of rocks. Do you see any gold coloring in any of the rocks?
Stage1 Question: Describe the large object near GZ, on top of the pile of slag.
To get to stage 2, you can follow the road until you are within 100 feet of the stage, then find and follow a short path to look down the side of the mountain of slag that you have been walking on.
Stage 2 Question: Stand on the top of the ridge and look down the steep slope. Describe what you see and hear at the bottom of the slope of rocks. Do you think that would be a good place to search for gold? Why?
Continue on up to stage 3. You can take several trails to get there.
Stage 3Hint: You may have already been here if you have done TDE #5 -- A Simpleton Critter
Stage 3: Question: You will go by Prescott mine here. Many original walls, made entirely with slag, are still standing. You will see another mountain of rocks behind it that have been drilled and shoveled out, much of it by hand. Judging by the types of rocks, is this a Hard Rock mine, or another type of mine?
Stage 4 Hint: You can get to Stage 4, or you might already have reached this spot by doing TDE #3 -- Lame Tailor Rim
To get to Stage 4 from Stage 3, you will walk past the visitors center, across the street into the overflow parking lot, and follow the path at the back around the slag to a path at the end of the column of slag that you can take to top of the rocky ridge. Climb up on the slag and walk about 50 yards looking for the large object on the left through the woods, less than 50 yards away. You could find a path to climb down and get over to the object. This was used as an anchor to pull the carts to move the massive amount of rocks away from the entry where they could be sorted. It shows what a physical challenge it was to move so much earth, especially when most of it is rock that was either hammered or dynamited.
Stage 4 Question: Describe the large man-made object used by man to help move immense amounts of rocks.
After finishing stage 4, make your way up to the road by the visitors center.
Waypoint 5: From the visitor center, walk down the path next to the road and check out a sign describing the ponds across the street, and how they treat the water to eliminate the mercury from the water.
You do not need to answer any questions here, but it is very interesting to read about how we are trying to make amends to the land and water. Continue on down to the parking spot. You will be walking right through the 2nd and 3rd level ponds.
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Other sources for information about the gold in grass valley:
Grass Valley Gold
Empire Mine Historic Park
Hard Rock Mining in Grass Valley
Gold Extraction Process
Here are the other caches in the series:
1. TDE #1 -- A Satin Roller
2. TDE #2 -- Analytic Alerts--Archived--
3. TDE #3 -- Lame Tailor Rim
4. TDE #4 -- Absolute Prior Loon--archived--
5. TDE #5 -- A Simpleton Critter
6. TDE # 6 -- Bipolar Onerous Lot-- archived--
7. TDE # 7 -- Trained India Girl--Archived
8. TDE # 8 -- Raider Nail Tiding
9. TDE # 9 -- Nail Hull In Riot--Archived
10. TDE # 10 -- Meanie Prep Smirk
11. TDE Finalee Bonus Cache -- Corncob Poorest Souls