One of the most intriguing maps that has been discovered is the Minas del Oro (Gold Mines) map. The original is leather, but for the sake of clarity, a drawn replica is shown below, compliments of Tom Kollenborn. The year that the map was created is either 1814, 1824, 1834 or 1844, as the third digit was worn off.
At first glance, this map seems to be looking west somehow, because of the label of Rio Salado (Salt River) and the “Picacho” would naturally be Weaver’s needle. But, the label of Rio Salado appeared to be incorrect, because most maps point north and the Salt River runs mostly east-west.
The map is trying to tell the viewer to look for a fold in the basalt and only one fold in the basalt was known; a hill (Cerro Negra) in the middle of the Molly Marie Prospect (a dome in the basalt with a breccia pipe).
It was conceived that this map was looking north, and the river was actually First Water Creek in First Water Canyon, not the Salt River, that flows at least 6 months of the year most years. It was also guessed that the “Picacho” was a spire by Government Well, about a mile to the northwest from the fold in the basalt. This is what the spire looks like:
Several hikes were made into First Water Canyon over many months, just because it was a nice hike, and on one hike out of the canyon, this was noticed in the gated road that leads from the awning area:
These were thought to be ox-cart ruts, from steel-rimmed wheels. After some research, it was learned that the awning area was built in the early 1970’s as a satellite operation of the original First Water ranch which was about a mile upstream. A small dozer was used to make a very steep road to get materials to the awning area; this was not negotiable by animal-drawn carts. The topsoil was disturbed, and the rain did the rest; the ruts that crosscut the dozer road were exposed over the years. A ladder and broom was taken there, the ruts were cleaned, and photos were taken from above. The area that is circled in the photo below shows where the steel rims (not wood) cut the rock. It is estimated that these ruts were made over a period of over 100 years due to dates on Spanish maps. It appears that heavy rains washed gravel constantly across the ruts, and then new ones were worn by the carts.
Below is a diagram showing the relation ship of the Prospect, First Water Canyon, the awning, Hackberry Spring, and the cart ruts.
It was known that the Peraltas have had to use mercury to process the bonanza gold. Without mercury, it is estimated that only about 50% of the gold would have been recovered. It is suggested that arrastras were used, but were only used for amalgamation. By 1600, Mexico had 400 animal powered stamp mills in operation, and it is reasoned that they had one here. The ore was crushed and amalgamated much more quickly than by arrastras alone.
To test the theory that great amounts of mercury were used, a mercury vapor detector was rented (below).
It was read that a shallow hole should be dug in the topsoil, and the air in the hole should be tested immediately. This was done at Potosi, Bolivia by others to test the soil there; this is one of the most mercury-polluted places on earth due to the silver mining and patio process. This is a link to a paper about the mercury study that was done there:
The same procedures were done near First Water Canyon and generally the same results were achieved as those at Potosi ! Below is a portion of a vapor detector database showing one of the soil testing sites at First Water and how the mercury values increased and dropped off in a shallow test hole:
Jerome Model: J405-0007
Serial Number: 405-00347
Date: 27-Oct-15 21:28:58
dd-MMM-yyyy hh:mm:ss Reading Units Temp-C
27-Oct-15 14:05:22 0.87 ug/m3 33.43
27-Oct-15 14:05:24 1.13 ug/m3 33.43
27-Oct-15 14:05:26 0.97 ug/m3 33.43
27-Oct-15 14:05:28 2.75 ug/m3 33.43
27-Oct-15 14:05:30 2.66 ug/m3 33.43
27-Oct-15 14:05:32 1.09 ug/m3 33.43
27-Oct-15 14:05:34 0.54 ug/m3 33.43
27-Oct-15 14:05:35 0 ug/m3 33.43
The phenomena was observed just like what had occurred at Potosi. The meter would read 0 or just above 500 nanograms, and then spike to 2000 to 3000 nanograms (2 to 3 micrograms), and drop down again. This occurred in several test holes.
A quote from the Potosi paper: “but the excavation of the topsoil causes an important release of the elemental vapor, reaching concentrations over 3000ng m−3.” Note: This is equivalent to 3 ug/m3 on the Jerome detector.
This is photo-diagram of the items learned in First Water Canyon near the awning area:
These items align well with what is shown on the Minas del Oro map. The main camp (Campo Mayor) was at Hackberry Spring. Sunlight never touches the bottom there due to the very high cliffs running east-west . Hackberry is quite the oasis, and the spring runs year around.
There were also very high readings in the air at First Water Ranch, and especially in the creek bed itself, upstream from the awning. It is thought that the the people that lived there and the cattle were sick most of the time from breathing and ingesting mercury. This is what the creek bed looks like there and would correspond to the area called “Placeras” on the map.
The creek bed appears to have been placered and all the gravel and rocks were removed long ago. There are no ore deposits upstream, and a theory was generated that at one time a lot of ore was processed without mercury, and the stream bed was cleaned to re-work the sand left behind. This would have been a placer, but for different reasons than usual. To test the theory, sand was pulled back from the higher pockets of sand until black sand was exposed on the bedrock. Then, a battery powered vacuum was used to suck the black sand up. The sand was taken home, panned down, and the magnetite was removed. What remained was manganese minerals and Golden Barite. The manganese minerals and the Barite have the same density and could not be separated in any way by panning. Some very tiny specks of amalgam could be seen. Barite is an important mineral found in IOCG deposits.
Below is a picture of Golden Barite from Leadville, Colorado.
Over this many-year long investigation, two different refraction seismic surveys were done. These will be discussed further on the Seismic Work page. In the diagram below is shown the Black Chlorite alteration and the seismic lines that indicate pits. Each line indicated had 24 geophones to complete the survey. This is the same place indicated on the Minas del Oro (Gold Mines) map that indicates the mines. There are several maps that show the location of the mines of the district, but the Minas del Oro map is the most comprehensive because it shows the location of the mill, the mines, the haul road, and the placers. It is believed that as time progressed, the area that was mined was expanded and the Peraltas began mining underground. Although a guess, it is estimated the date on the map would be 1824. There is no doubt that the Minas del Oro map depicts the situation at that time exactly.