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Hello all, it’s Random Scientist Inc. I recently paid a visit to southwestern Utah, also known as Utah’s Dixie and Utah’s Sandstone Country. While there, I did some prospecting for fossils (and, admittedly, silver, since silver has been discovered in the sandstone formations near Silver Reef, which is just 15 minutes north of St. George along I-15), and while I didn’t find anything fossil- or silver-wise, I was able to study the geology of the area. Before I discuss the geology of the area, though, I feel a description of the geography of the Silver Reef area is appropriate.
To view the geography of the area, please go to http://maps.google.com and type “silver reef utah” in the search box. Silver Reef is located near the northern tip of the visible portion of the White Reef, which is the most prominent reef in the area. Its visible portion in the Silver Reef area extends a total of 15 miles, although the reef is actually over 100 miles long. Most of the reef is located underground, but this particular section of the reef was brought up by seismic forces which caused a 15 mile portion of the sandstone formation to rise from the ground and stand on its side. The formations are called “reefs” because they resemble ocean reefs. The White Reef and the Buckeye Reef, which will be discussed in the next paragraph, are made of Navajo Sandstone, which is naturally white-ish in appearance. The East Reef, which will be described later in this post, is made of the typical red sandstone of the area. Within a ten-mile radius of Silver Reef, the towns of Harrisburg, Leeds, Toquerville, Pintura, and Washington can be found. West of Silver Reef is the Pine Valley Mountains, most of which are part of Dixie National Forest. Red Cliffs Recreation Area is south of Silver Reef, west of Harrisburg.
Now for the geology of the Silver Reef area. The White Reef, the most prominent “reef” in the area, was formed hundreds of thousands of years ago, when earthquakes along the Hurricane Fault (which is still an active fault today) forced a section of Navajo Sandstone 15 miles long (longitudinally-aligned) to the surface. Several smaller segments of Navajo Sandstone were also forced to the surface, although none as prominent as the main White Reef. The formation of the Buckeye Reef is somewhat controversial. Some believe it is an extension of the White Reef, while others believe that it is a separate formation altogether. There was a large debate on this during Silver Reef’s heyday (1877-1900), and it was eventually decided by the geologists of the area that the Buckeye Reef was not an extension of the White Reef. Further studies on the matter were inconclusive, although some still believe that the White Reef and the Buckeye Reef are of the same formation. These people also believe that the geologists came to the conclusion they did because, if the Buckeye Reef was part of the White Reef, the Stormont Mining Company, which largely operated mines on the Buckeye Reef, and the Christy Mining Company, which largely operated mines on the White Reef, would go into a legal battle over ownership of the mines. The East Reef was formed separate from the White and Buckeye reefs, as it is just barely southwest of Toquerville. The East Reef was not brought to the surface by seismic forces; rather, it formed as most sandstone formations do. Silver has not been found in abundance on this reef, but a couple mines (the Vanderbilt being the most productive) were opened on this reef, and they will be described in a later post.
The silver was deposited in the area before the reefs were forced to the surface, when water carried sediments, silver, dead plants, and some dead animals to the area where the sandstone formations were eventually formed. Over time, the sandstone formations, saturated with silver, were formed, and millions of years later these formations were forced to the surface by seismic activity. Strangely, silver can also be found in the petrified wood and occasionally the fossils that are abundant in the sedimentary sandstone. Most of the silver found in fossils was sparse and low-grade, while the silver found in the sandstone and the petrified wood was plentiful and of a high grade. Copper and, strangely, some uranium was deposited in the same formations, and amalgamation (processing) of the silver wasn’t as successful due to the high copper content. The uranium was discovered in 1880, and was mined in the 1950s. We’ll look into that more later.
The silver in the area averaged .888 in fineness, on account of the copper. In the Buckeye Reef, where the copper was less abundant, the silver averaged slightly higher in fineness, at about .930. The finest silver taken from the area (of course taken from the Buckeye Reef) assayed about .980 in fineness. On account of the copper, only about 65-70 percent of the silver found could be processed, but as time went on and improvements in the mills were made, this percentage went up to about 75-80 percent. In the Stormont Mill, where the Virgin River provided power for the ten-stamp mill, about 80-85 percent of the silver was taken from the sandstone that had been mined. When the uranium was discovered in 1880, it was discarded, as at the time it had little value or use. As mentioned earlier, information regarding the uranium found in the area will be published later.
In my next post, I will discuss the major mines in the area, starting on the northern tip of the White Reef and working south. In another post, I will discuss the major mines of the Buckeye Reef. Stay tuned for more on the Silver Reef Sandstone District!
Random Scientist Inc.
So... what do you think? Please leave me a comment.
