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Researching a Depression Era Mine – Part I: Mine Overview

No one can say with certainty how many adits and shafts have been dug in Arizona’s mining districts in historic times. Estimates vary considerably – even between state and federal agencies – but could range as high as 100,000 hard rock mine entrances. The vast majority fall into two broad categories: “past producers” and “prospects” and nearly all of them are now abandoned. The steady decline in gold and silver production during the 1920’s and early 1930’s led to the closing of many mines. Settlements were dismantled, or simply abandoned; as people moved on to seek their livelihood elsewhere.

After the earlier pioneer period, another wave of migration occurred following the economic collapse and ensuing depression of the 1930’s. These were jobless and homeless men and families. For some of them, their attraction to the mining districts was the based upon the hope that a few ounces of gold each month could keep them fed. For others, a lode claim provided a cheap way to live on the land – whether there was any ore or not. [Note 1]

Within a one mile radius of Morgan Butte peak [Note 2], there are more than sixteen mine shafts and adits. If you extend your search area to a radius of barely two and a half miles, there are several dozens of old mines and associated settlements. Although some of them date to the late 1800’s (and a few were good producers), the majority were established in the era that extended from the early 1900’s to the Great Depression of the 1930’s. Unfortunately, the geology in this locale virtually guaranteed that most mines would turn out to be a disappointment. While there were many promising signs of ore, nature conspired to place much of it in small pockets and seams. What might appear to be high grade ore in an exposed vein could abruptly end after only fifty feet. More frequently, the vein contained low grade ore that could not offset the cost of extraction and processing for a small time operator.

Without investors, the only way to make a go of it at a low producing mine was to have little or no capital burden. This article will focus on a mine and small settlement near Morgan Butte that fits this broad characterization: It was a low producer, there was no mill or heavy equipment and, from appearances, there was virtually no operating overhead. Moreover, the features at this mine suggest that it was worked during the 1930’s. By that time, most of the successful mines in the area had already run their course.

A Depression Era Mine

The subject of this article is a mine located about .75 miles NNE of Morgan Butte, roughly 36 degrees east of true north from the peak [Note 3]. This area is literally blanketed with old (closed) and active lode mining claims and it includes a patchwork of patented land that is now deeded to modern day ranchers and investors.

We have discussed on previous occasions the use of arrastres. They were the “poor man’s mill” – a way to cheaply pulverize silver or gold bearing rock. The rate of processing would be limited to only a few hundred pounds of rock over a period of several days. Typically, an arrastre would add mercury to the ore charge to produce an amalgam. The older “Mexican” arrastres around Wickenburg were constructed using shaped stone in the walls and floor and did not use mortar or cement. Notice the more modern style of the arrastre at this site:

Figure 1
Figure 1, Depression Era Arrastre

Figure 1 shows an arrastre that is quite tall by normal standards, but which has a relatively narrow inner diameter. It was constructed with cement and boulders to a height of more than three feet. The area surrounding the arrastre is still quite flat and afforded ample space for a mule to pull the drag stone that crushed the ore charge.

Arrastres of this type can generally be classified as post-1900. In this example however, I believe it dates to the 1930’s, but not more than one decade earlier. More on that subject later.

Figure 2
Figure 2, Top View of Arrastre

Figure 2 shows an inside view of the arrastre. The interior wall was fully encased with cement and the metal center post is, if anything, over engineered. The floor was built using stonework in the traditional manner. This is probably because a cement floor could not have withstood the abrasive effects of the drag-stone. The width of the floor was wide enough to accommodate a single drag stone – suggesting that only two or three hundred pounds of ore was processed during each cycle.

There are two particularly interesting features in the interior of the arrastre. First, notice the two drain pipes to the right of center. The lower pipe is in a metal plate, while the upper pipe protrudes through the wall to the left. Second, notice the abrasion and water marks on the center column and inner wall.

There were several steps involved in the pulverizing and amalgamation process. Once the ore charge had been thoroughly reduced to a fine sandy texture, water would be added to produce a fluid, muddy consistency. At that point, mercury would be added and the drag-stone operation might continue for another few days. This was a critical point in the mixing of the ore/sand/mercury. The objective was to continually mix the components so that amalgamation (a chemical bonding between the ore and mercury) would occur.

Finally, more water would be added (that is, to the level of the upper pipe) to produce a ‘soupy’ texture while the mule would continue to pull the drag stone, but at a slower rate. This would permit the amalgam to slowly settle to the bottom of the arrastre. The water would then be drained away and the waste material would be scooped out. The ore (gold or silver) would have settled on the floor, where it could be removed and separated from the mercury.

Figure 3
Figure 3, Drag Stone with Cable

Further evidence that this arrastre dates to the early decades of the 1900’s is provided in Figure 3. Notice that this drag stone has a steel cable inserted on the top. Older, ‘Mexican’ arrastres used drag stones that typically weighed more than 200 pounds and featured a bent iron rod protruding from the top. I have never seen an ‘old’ arrastre (one that can be dated to the 1800’s) that used steel cable. [Note 4] Aside from the use of this more modern feature, the drag stone does not weigh much more than 100 pounds.

Figure 4
Figure 4, Another Drag Stone with Cable

Figure 4 shows another drag stone at the arrastre. Like the previous one, it used a steel cable to connect to the rotating arm that was pulled by a mule or horse. In this case, the stone is nearly the width of the drag area inside the arrastre. Notice that five edge faces of this stone and the bottom have been worn smooth from use. There are relatively few drag stones at this site (only four that I have confirmed). Considering the relatively small capacity of the arrastre and the nature of the mine, I believe it was not used continuously. Otherwise, there would be more drag stones.

There are two unanswered questions in the views of the arrastre. What was the source of water and, importantly, did this arrastre use mercury for amalgamation?
Figure 5
Figure 5, Wet Panning Site above Arrastre

There is a rather ingenious site approximately 100 yards above the arrastre that was used for separating ore from pulverized waste. Figure 5 shows a rock and cement structure that features a high wall, a ledge, two troughs and a drainage sluice (center of photo). This is the functional equivalent of a “panning” site that would have used water motion to separate the heavier gold ore from the lighter waste material. The design of this structure suggests to me that the arrastre did not rely upon mercury for amalgamation. In other words, the arrastre pulverized the ore bearing rocks and the “panning” site completed the separation of ore from waste material.

Another fifty feet or so beyond this structure there is a spring and well (perhaps more properly described as a cistern) that collected water for the arrastre and the washing/panning structure. See Figure 6.

Figure 6
Figure 6, Well/Cistern

Today, it serves as an occasional source of water for cattle in this section of land. The rancher has protected the opening to limit the inflow of debris. Not clearly visible, but importantly present, there is a metal ore car rail on the left side of the well opening. A feature such as this suggests that at least one of the three adits at this mine may have had rail tracks and an ore car. I have found no other rails outside the mine entrances, but tracks may remain in the interior of the mine.

When I examined the well site, the water level was several feet deep and was clear. Decadal drought conditions have reduced the flow of water, but would still provide ample volume via gravity feed to the arrastre, panning area and modern water trough. There are old metal and modern PCV pipes running down the gulch that show the original and modern uses of the well. Seasonal rains certainly contribute to the water level and probably produce some rather significant runoff in this steep and narrow gulch.

Figure 7
Figure 7, Upper Adit

This mine certainly qualified as a “hard rock” operation. As shown in Figure 7, the upper adit (one of three entrances) was dug and blasted into a very solid face of the mountain. The adit gives an appearance of a gentle slope in a westerly direction. The gangue pile in front of the adit indicates that a sizable quantity of rock was removed to reach the primary ore vein. I have not entered this adit and I do not suggest that you do, either – it may serve as habitat for snakes and other wildlife. Furthermore, it is not possible to assess the condition beyond the first few feet. The sizable boulders at the entrance show that rock has sloughed off the wall above the mine.

Figure 8
Figure 8, Second Adit

Figure 8 shows the second adit, west of the one in Figure 7. Judging from their width, both adits probably contained narrow veins of ore. I found no evidence of copper in the first dump and it is likely that this mine was chasing a vein of gold. This adit is characteristic of the rock formations commonly found in the area. The adit literally follows the slope and angle of the vein. The height and width of the adit was very conservative – that is, you could not enter without stooping, and the width at the entrance is not more than thirty inches.

Figure 9
Figure 9, Entrance to Adit 3

Figure 9 shows the entrance to the third adit, which is farther west of Figure 8. This is the only gated entrance at the mine site. It is again apparent that the entrance is quite small. The presence of the gate may indicate that a winze (vertical shaft connecting different levels of adits) lies beyond the entrance. Although one of my hiking partners is examining the entrance, we did not go beyond this opening. There is a rather sizable dump to the right of the photo that contains a few hundred tons of waste rock.

Notice that two of these adits have structures built with wood posts, boards and planks. They appear to be in generally good condition. Each adit is protected by steep (nearly vertical) walls in this gulch, which has probably protected the wood from rapid weathering.

Assessment

An evaluation of the first nine photos suggests the following:

  1. The manner of construction of the arrastre clearly indicates the use of more modern materials than are found at the older, traditional “Mexican” arrastres.
  2. Although the wall was unusually high, the capacity for pulverizing ore was quite limited due to the narrow inner dimensions.
  3. Steel cables were not used for pulling drag rocks in the 1800’s or at any earlier point in time.
  4. There is no convincing evidence that mercury was used at the arrastre. Instead, it is likely that the pulverized ore was taken to the “panning” site shown in Figure 5 where it could be gently washed to separate gold from the waste material.
  5. The adits at this mine were quite small. The development of this mine shows considerable economy in effort and expense. In other words, the adits were “just wide enough” to get the job done.
  6. In comparison to mines that were high producers of ore, the dumps at this site are not very large. This correlates with the small dimensions of the adits, but also suggests that the tunnels and drifts were not extensive. The “pay streak” at this mine, such as it was, must have been very narrow.
  7. Given the low-budget nature of this site, the recovery of a few ounces of gold each month could have kept this operation going.

Part 2 of this two-part series, provides observations about living conditions, as well as historical context and information on how to find the site.

Notes

  1. There are quite a number of mine shafts in the area east of Wickenburg that are only eight to 15 feet in depth. In most cases, there is little evidence of useful results. Many of these were “squatter” prospects. Others gave only the appearance of being a legitimate mining operation. Ranchers in this area have told me there were several thousand people living in the open desert and at old settlements during the Depression.
  2. USGS Morgan Butte Quadrangle map. Morgan Butte is located at N 34D 03′ 03″ by W 112D 33′ 06″ (WGS84). See sections 1-4 and 9-12 as the primary reference area in this article.
  3. Here are two sets of GPS coordinates. The first is for one of the adits and the second set is for the arrastre: Upper adit – N 34D 03′ 24″ by W 112D 32′ 49″. Arrastre – N 34D 03′ 35″ by W 112D 32′ 38″.
  4. Steel cable (also known as wire rope) was first developed in the 1830’s by a German mining engineer named Wilhelm Albert and came into use in the late nineteenth century for hoisting heavy loads in deep mines. The early versions were a combination of wire wrapped around rope, hence the name “wire rope.” The cables shown in this article do not match the type of cable used in the latter portion of the 1800’s.

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