Wednesday, September 7, 2016

Shafer Museum, Winthrop, WA

Shafer Museum
Winthrop, WA
August 16, 2016  
My wife and I visited the Shafer Museum in Winthrop, Washington this summer. I was told about this museum by a fellow volunteer who was very impressed with all of their exhibits. While traveling the northwestern states on a vacation this summer I thought that I would check it out. I have spent many years traveling in our country investigating stamp mills, but never knew there was so much mining activity in the state of Washington. I called the museum several months prior to taking the vacation and talked with the  staff. At that time they told me they had several stamp mills on site and one of the 2-stamp mills they periodically operated. This was a homemade machine and I was excited to see it and the other mills.
When I arrived I met with three of the museum staff that were involved with the outside equipment that included many mining artifacts. The town of Winthrop is in northern Washington, about 185 miles North West of Spokane. I was very impressed with the amount of mining artifacts, especially the stamp mills. My first question was where did all of the stamp mills and other mining artifacts come from? I have not seen that many artifacts from a centralized local area in one museum anywhere. They said that they were all from the  area of the Methow Valley that was comprised of three local mining districts including Slate Creek, Squaw Creek and Twisp Mining Districts. I was amazed with the number of artifacts that survived the years. They attributed part of their success from the support of the Forest Service that allowed them to recover the artifacts and set them up on the museum site. The picture below shows the three tour guides and my friend that told be about the museum. They are in front of one of the many mining buildings on the property.

They gave us a guided tour of the mining artifacts and it was very informative. The following are details of the tour of the depository of stamp mills:

8-Stamp “Circular” Mill The first component below (left) is a rare 8-Stamp Mill. This artifact did not have a label on it, but it is probably made at Straub Manufacturing Co. in Oakland, California. Most horizontal stamp mills were set in a straight line as seen in the rest of the mining displays. However, in this case the mill was constructed with the stamps in a circle being activated with a vertical incline wedge instead of the horizontal cam system to raise and drop the stamps to crush the ore. The picture below (left) shows the stamp mill without the shroud around the bottom of the mill. There are additional weights on the top of each stamp in increase the crushing capability of the mill. The drive pulley is sticking out of the top on the guide where there is a gear that rotates the incline wedge to lift and drop the stamps.
This mill was used for testing areas that had gold production potential. It was in high demand since it was very portable and could be disassembled and loaded on burros and transported to remote areas to test ores on claims that might become mines in the future.

2-Stamp “homemade” mill The picture above (right) was made by a miner that shows the ingenuity of the miners back in the day. You can see they used the items available to them at the time. You will notice the base of the mill is a movable jaw out of a large jaw crusher. The uprights were pieces of heavy duty angle iron attached to channel steel and the stamps were heavy gauge pipe with steel caps to add to the weight of the stamps. All of the parts except for the crusher jaw and drive pulley were probably made by the miner on the mill site.

3-Stamp Mill and Components Illustration The slide below shows a picture of a mill building (right) and a drawing of the gold separation process (left). This gives you an idea of what the process was and what it looked like back in the day.

3-Stamp Mill Setup at the museum The picture (below) shows the 3-stamper setup at the museum, mimicking the above drawing and layout. The next slides after this are parts of the separating process that was used to extract the gold.

Joshua Hendy 3-Stamp Mill  The picture (below) shows an overview of the stamp mill with the various components including the drive pulley's uprights and the individual mortar boxes. This is an impressive machine!

3-Stamp Mill Mortar Box Closeup The picture (below) shows a closeup of the 3-stamp Joshua Hendy stamp mill with individual mortar boxes that have a triple discharge. The material flows out three of the sides of each mortar box. The triple discharge was a big thing, since this mill could put out significantly more crushed material than the standard 3-stamper. This was a big selling point for these special machines.

Sluice Table The picture (above) shows a board with holes drilled in it across the bottom of the outlet of the mortar boxes that distributes the water to the next separation component that is called the sluice table. The table, not shown, is made of copper and was coated with mercury to capture the fine gold particles. The table would pick up about 40% to 50% of the free gold before it went to the next component known as the Muller Pan.

Shaker Table Once the concentrates passed through the Muller Pan it would go on to the Shaker Table (below). This device shakes, hence the reason for its name, and the gold would be separated from the gangue “waste" materials and collected at the foot of the table. This increased the capture of the larger pieces of gold that would not be caught by the mercury. The larger pieces of gold would not stick to the amalgam as they would just pass over the table. The table would probably get another 20% to 40% of the remaining gold out of the concentrates.

Vaner Table The remaining concentrates would then be distributed on the Vaner Table (below) and most of the remaining gold would be separated from the concentrates. The left over material would be distributed to the distribution box on the table that has a fiber belt to aid in separation. This concludes the discussion of the three processes that would remove most of the free gold from the concentrates. They are the sluice table, shaker table and the Vaner.


1 comment:

  1. This is the first stamp mill I got to see 'close up and personal'. I'm glad you made the drive, hope you enjoyed the trip.