The Great Mine

The greatest challenge during the search for the lost Peralta Mines has been coming to grips with just how big the mining operations actually were. The cart ruts told of countless loads of ore going to First Water Canyon, but it didn’t completely “sink in”.

Cerro Negra was pored over, trying to gain more understanding of the orebody and the mining that took place there. Dozens of rocks were gathered, cut, stared at with a loupe, outcrops were photographed, etc.  It was known that the gossan breccias, high in Lithium, and the quartz veinlets were the keys.  Finally it was determined that the Prospect was one large IOCG deposit with “vents” to the brine lake floor rather then several VMS deposits.

While looking at Cerro Negra with Google earth and rotating the view to look south,  the full magnificence of the mining that had taken place was seen that had taken place, and it was breathtaking.

The “Great Mine” north of the Superstitions was described in the Phoenix Herald and Republican in 1893.  Joe Ribaudo discovered the article in the book “Arizona, the Last Frontier”, by Joseph Miller. Here is an excerpt from the newspaper article:

“Over on the north side of this wonderful mountain so peculiar in shape, standing like the ruins of some great walled city with its tall spires and huge monuments, there has been discovered an ancient mining camp. Whether this mining was done by the Indians and Mexicans of the last century, or whether the operations date to years when de Vaca and Black Stephen started from the coast of Florida to find the gold fields toward the setting sun, may never be known. It is certain, however, that there are shafts and tunnels and drifts and stopes and the clearly-defined walls of a great mine. On the dumps are found tons of rock which without doubt came out of these workings.”

The description is of an underground mine, but how can you see the walls of an underground mine? It is surmised that the only thing it could be referring to is “subsidence” or the “cave zone”. The article said the prospectors found the mine in 1888, and they went on to find ore much richer in the Goldfield area. If this large cave zone was seen it 1888, it certain that it is still able to be seen today, even if erosion has taken place?

The only mining method available in the mid-1800’s and earlier for mining bulk ore was the top-slicing method. This was the precursor to block-caving and top-slicing was used at Inspiration and Morenci, Arizona.

The Cerro Negra orebody was formed under a layer of basalt, about 100 feet thick, but there is still abundant jasper, and jasperoid that vented through the basalt to the surface.

This is photo below is looking south towards the Cerro Negra ore body. Much of the center of the uppermost portion of of the deposit has been removed that is nearby the rhyolite, forming a deep subsidence zone; It is guessed that a thickness between 20 to 40 feet was mined. It appears that they focused on the richest supergene ore beneath the drainages.

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The Cave Zone of the “Great Mine” looking South

This is what the rhyolite looks like. It resembles the “Imperial porphyry” of Rome

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Rhyolite Porphyry

There is definite proof of subsidence, and this is on the ridge just north of Cerro Negra (the photo is looking south). This probably appeared long after 1848, after the timber posts and matt rotted and compressed. These are beds of silicified tuff that are tipped upwards; their edges are not eroded (Flatiron is in the background).

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West side of Cave Zone looking South

Even though a lot of mining took place here, they still barely scratched the surface.

One map depicts the mine very well, in typical Spanish style, and actually shows the cave zone. This appeared about 1895 (thanks again, Tom Kollenborn). It is the Hoddenplye Map. (Note the tiny hole through the top of the mountain, again)

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Hoddenplye Map

The “breccia dike” labeled on the photo above is about 10 feet wide. It looks knobby, and pretty blah in the field due to oxidation, but below is a photo of what some of this rock looks like after it is cut; it is jasper and chlorite. There are large cobbles of jasperoid in the dike also.

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The spot labeled “portal” in the photo had bees flying out from beneath large rocks during the worst of the recent drought. They were going for water. A hole was dug down at the rock face above the bee hole and the brow of a tunnel is believed to have been reached with a shovel; there was a great stash of saguaro fruit there from pack rats, so there is a significant void.

It is believed that this is the portal indicated on the Ortiz Map below (thanks again Tom Kollenborn). If it is orientated the same as the diagram above, it can be seen that they had several tunnels into the caved zone, and they explored extensively along the rhyolite front.  It is believed that some of these tunnels were used to assist in draining water after the exploration and delineation.

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Ortiz Map

Ironically, the first time the author ever stepped foot in the “cave zone” was about 12 years ago.  It was  known that it was something good, but had no knowledge of VMS deposits, and it wasn’t even known that the neck of the volcano was only about 200 feet away.

10 contiguous claims were held at the time, and felt it extremely important to put a claim on this ground, so unknowingly put the center of claim marker #11 right in the middle of the cave zone, creating a claim separate from the rest. That one claim, at the same bearing N20W as the other 10, covered almost the entire deposit and aligned perfectly with the cave zone it is now known.

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Burbridge Map

From almost the time #11 was staked, the author has believed that the satellite workings on the right side of the Burbridge map (thanks again Tom Kollenborn) were at Cerro Negra, but could not “see” before discovering the cave zone the relationship and alignment. It is known now (see the bottom of this article) that the satellite workings are on the contact zone of the Rhyolite.

It has always been the author’s belief that the Burbridge Map with the title, “The Esteemed People of the Salt River District of the North” was a map of an exploration project. The original was dated by the U of A as truly being from the 18th century. Considering the Spanish drove a tunnel several miles long to drain the mines of Pachuca in the 18th century, this really was “light work” for them.

Where the crew of Mandozo Segundo Marzo drove their tunnels and sunk shafts in 1753 is likely where the cave zone is today. They simply blocked out the ore for others to follow, and it took almost 100 years to create the cave zone that remains today.

Below is a diagram of the old top-slicing mining method. If this is indeed a cave zone shown above, this is how they did it. This takes quite a bit of timber, and the Peralta’s did not have much nearby. This must have been the number one limitation regarding the amount of tons they could mine from underground.

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Below is a photo of the cave zone next to the saddle area. In the background can be seen El Sombrero at the bearing of S65E. It appears like the rock over the stope is STILL subsiding even today on the sides of the cave zone as the decayed timber mat is crushed below.

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A layer of basalt covers the deposit, and jasper, jasperoid, and some gossan has been ejected through the basalt. The ejected material can be found in large quantities today. Because of the abundant limestone cobbles that were beneath the basalt before the IOCG was formed, jasperoid replaced the limestone, and some jasperoid cobbles have been ejected also.

This is what a cut piece of the jasperoid looks like from the breccia dike described above:

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To lead into another aspect of the “Great Mine” subject, below is the Bicknell article that was published in 1895.

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The part of the story that is most unbelievable is where they abandoned the shaft that was being mined by the Mexicans, after they threw the bodies inside, and then they saunter on down the hill and find an outcrop of auriferous quartz.   It is not completely clear though from Bicknell’s writing whether they find a second shaft or not, or start from scratch.

It would seem plausible that if they found a quartz outcrop in say 1868?, and it was fairly large, it would still be there today, unless this happened in Goldfield? How could anything like this escape the eyes of so many for so long and be right out in the open?

The possibility of something like this really exists.

Below is a photo again of the cave zone with the location of a vein and breccia pipe added. This vein has a strike length of over 150’, and its width is about 15 feet wide (really). This is interpreted as the auriferous siliceous pipe shown in the Kuroko diagram above. There are dozens of other narrower quartz veins in the cave zone.

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The breccia pipe is made entirely of the material in the photo below. It is laced with drusy quartz, and copper staining can be seen with a loupe.

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These are large quartz crystals covered by chalcedony on the vein that outcrops:

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In conclusion, it is very possible that the stories of old could have happened nearly exactly as they were told.

Sims Ely wrote the first book about lost mines or “lost mine” in the Superstition Mountains, and he coined the phrase “the lost Dutchman” with the title of his book, the “The Lost Dutchman Mine”. In his lifetime of searching for the mine, he did not find much physical evidence, but he found 40 acres of mesquite stumps near LeBarge Canyon (he spelled it that way) in about the year 1900? He found the diameters and the density of the mesquite remarkable in that the Superstitions were very lacking in trees of this quality. He researched the possibilities, and came to the conclusion that the trees were used in the mine he had been looking for.

Sims was not a mining man, and he wondered what kind of mine would use that many mesquite trees. The square-set mining method, which uses a lot of timber, was not invented until well after 1848, and it needs straight, and much larger timber. This miner offers that the twisted trunks of the mesquite, that are not big enough for timber, were only good for the mining method described above, the top slice method. Their intertwined trunks would have worked fairly well to make the timber mat for the technique.

It is not known precisely where the “soldier camp” is that Sims said the stumps were found, but it appears to be about 3 to 4 miles east of the “Great Mine”. It appears that neither the “Great Mine” or the stumps could have existed without the other.

Once the conclusion was drawn that the Prospect was on large IOCG deposit, things began to click. There has to be lots of magnetite for this to be an IOCG. A small, but powerful Neodymium magnet on a string was used to conduct a magnetic survey of sorts on the ground.  First, it was learned that all of the soil in Area 1 was loaded with magnetite.  Just by kicking any dirt to loosen it and placing the magnet down brought instant results.  It was clear that the basalt that once covered the breccias was dissolved and leached into the ground.

http://mollymarieprospect.com/IOCG/magnetdirt.JPG
Area 1 Magnetic Soil

By testing the basalt around Cerro Negra it was learned that there was a zone of highly magnetite-enriched basalt near its base.  The next 2 photos show what some of it looks like.  Some of the magnetite-altered basalt is very red inundated with swarms of tiny veinlets of quartz.

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Highly Magnetite-Enriched Basalt (glows red under SW UV)
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Highly Magnetite-Enriched Basalt

Finally, finally, it was thought to place the Burbridge map over an enhanced photo of Cerro Negra.  It is thought that there is with about 95% certainty that this is exactly what the Burbridge map was describing.  Note the workings on the edge of the Rhyolite that are below a drainage to explore or mine for supergene gold.  Perfect combination. Note also the red magnetite-enriched zones that were accessed (very magnetic in the field).  Google Earth does not do well showing vertical relief, but in the field deep zones of subsidence have shafts near them on the south, west, and north sides.   No wonder the map described in the Salazar Survey gave the exact directions to the top of Cerro Negra.

http://mollymarieprospect.com/IOCG/square2011wmap2.jpg
The Rest of the Great Mine

The Callejon, or “Straight Pass” also matches perfectly.  The Pass can be seen in the photo below in the caved zone.  The photo does not really do it justice, as it is pretty neat to walk across this saddle in the field.

http://mollymarieprospect.com/IOCG/callejon.JPG
Callejon (The Straight Pass) in the mIddle of the Caved Zone

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