During my mining career, I have always been fascinated by Bonanza gold ore, how the wonderful rock was formed, and how and where it has occurred.
The richest gold mine in the world for decades was the Little Jonny Mine (or Ibex) in Leadville, Colorado (about 1893 to the 1930’s). The Superintendent of the mine was the husband of the “Unsinkable Molly Brown”. Below is a photo of the mine at timberline (12,000 feet):
Below is a write-up about the mine:
“During Campion's days, miners found the 'golden stairs' and ‘millionaire's chamber on the third level between Numbers 1 and 2 shafts of the Ibex (Number 1 was the Little Jonny). The stairs – a step fault – had wire and sheet gold; the chamber - a cave – was similarly inlaid. “It (the gold) could be pried off with a chisel or screwdriver,' said one observer” (Gilfillan, 1964).
Emmons (1927) describes another find as follows: "Wire and leaf gold occurred very abundantly in a seam of sulfide which was found on the sixth level of the Ibex about 200 feet south of the Big Four shaft and which was associated with certain highly siliceous ores interbedded with black ‘Weber shales.' Some of the richest ore found in the Ibex mine was taken from this locality. The oxidized siliceous ore in one of the stopes above the third level of the same mine contained a small but remarkably rich seam of leaf and wire gold mingled with decomposed silicified porphyry. Sixteen sacks mined from this seam carried more than 50 percent of gold. In a specimen from this locality, seen in the office of the Ibex Mining Co., the gold occurs in a seam of compact jasperoid between limestone and porphyry. The jasperoid is stained deep brown by iron, has a conchoidal fracture, and contains sheets of gold in the joints. Some of these sheets are from 1 to 2 inches across. The gold is pure yellow and 860 fine. Another specimen in the company's office, from the sixth level of the Ibex mine, shows a large cluster of zinc blende and pyrite crystals which form a coating half an inch thick on a quartz seam. The quartz, partly stained by oxidation, shows many irregular openings which contain free gold, mostly in long wires but partly in leaf-like plates.”
Sound familiar? A similar cave was found at the Cresson Mine in Cripple Creek. Below is a piece of gold ore from the Little Jonny (24 ounces)
I worked at the Black Cloud Mine for over 8 years, which was about 1 mile away from the Little Jonny. A retired miner I knew was raised in Jonnytown near the mine, and he said as a boy he saw 2 miners carrying what looked like a cabbage head of gold in a dynamite box to the mine office to get locked up in the safe. The Black Cloud was a lead-zinc-silver-gold mine without the bonanza gold, but one time a contracted driller cored through a half inch vein of pure gold, and he gave the core to the General Manager. The GM split the core and gave the driller half of it for his honesty. It was a beautiful specimen.
One evening after work at “The Cloud”, I was informed that a woman named Mary Ann Sadar (80 years old) had 2-5 gallon buckets of concentrate she wanted someone to look at. I was told that her late husband was the mill superintendent at the Little Jonny. I was very interested. She gave a friend of mine and myself two buckets of jig concentrates (sand), two small full jars which she said were silver nuggets and a another jar which had 3 golf ball sized chunks of what she called “silver amalgam”. We agreed to split any proceeds 50/50. To make a long story short, we processed the material into small bars, it was almost all gold (25 ounces), and we gave her a check for 5,000 dollars. It kind of took her breath away. It was kind of cool being loosely associated with the Titanic thread.
So how about the Peralta Mines? It is known where they were located, and an IOCG (Iron Oxide Copper Gold) deposit is located there, but the paradox is that IOCG deposits are not known for bonanza gold, and the Peralta’s had to be mining the type of stupid-rich ore that is described above. What was the mechanism that made the ore they mined so rich if it can’t be an IOCG type deposit?
Finally, there was a break in the case. There is a conical shaped hill on the north side of the Molly Marie Prospect that I have pored over for years off and on. I thought it was just silicified basalt, and finally I had an epiphany………. the hill was a sub-sea hydrothermal silica-hematite mound (vent) composed almost entirely of silica (quartz). There was another large one right next to it. I knew that there was a vent in the area because of the abundant banded jasper (jaspillite) found, but I guess the reason it took so long to figure it out is because I just couldn’t accept the fact that something so large, rare, and important could be undiscovered. This is what the hill looks like from the Needle Overlook parking lot (it’s the hill on the left).
A light came on, and armed with this concept, I decided to look at all the basalt on the property, very carefully. Lo and behold, about half of the mapped “basalt” on the claims is not basalt at all, but basalt covered with hydrothermal mounds of silica (quartz) rich in hematite. There in an entire FIELD of hydrothermal silica mounds! This in itself was not a shocker considering the IOCG deposit formed under a brine lake and there was a great amount of hydrothermal activity. The shocker is that I had walked over the basalt literally thousands of times and it hadn’t clicked! I have not been able to find even one instance of an IOCG that has been found in the world that is this complete, with the silica mounds, but it seems logical that all IOCG’s would have them before erosion takes place. This a photo of one of the smaller mounds that has been partially eroded.
This is a photo of a piece of the silica that has been sawn:
In defense of myself and the oodles of prospectors that have crossed the area, there is strange phenomenon regarding these silica mounds that must have caused others to miss this also for over 130 years. First, a piece of the silica must be crushed to powder with a mortar and pestle or other device; prospectors used to do this in lieu of fire assaying. Some of the crushed silica is a light gray and some is pink because of the hematite. Most of the silica is very brittle. I use a piece of window screen to separate the larger material when I use a mortar to make sure all of the rock is pulverized. Then, the sand must be rinsed in the pan until the gray or pink cloudiness is gone. Don’t let any of the sand out of the pan. Now drain just the water out of the pan. What remains looks like an entire pan of black sand. Now, try a magnet on it. It isn’t magnetic! (there is a little magnetite at the bottom). I think that is where the old timers quit. They thought, “hell, this is just basalt”, and threw the stuff away. Not so fast. under a 20x loupe, it is revealed that the sand is pure clear silica (quartz), but each grain is at least partially coated with black manganese. Much of the manganese has been knocked off, but the quartz grains are clear, and the manganese behind is projected through the un-magnified clear grains making it all of it look very black!
Below is a pan of the black material:
This is what the sand looks like up close:
I remembered that I had sampled two of the mounds (even though I didn’t know what they were at the time) and went back through some old records and found the fire assays from Jacobs Assaying in Tucson from about 15 years ago and a map that was made to show their location. They assayed significant gold, but not bonanza gold of course. The bonanza gold is at the base of the larger mounds, concentrated and deposited by supergene enrichment. It is extremely ironic that 3 of the samples that ran significant gold were located on the mound where the Ortiz tunnel terminates to the west where there is an obvious subsidence zone through the center of the mound that appears to be located on the feeder structure for the mound. The small oval on the western side is the subsidence zone.
There are more photos of the silica, etc. on the opening page of my website:
https://mollymarieprospect.com/
And, the conclusion page has been greatly expanded summarize the work that has been done and the discoveries that have been made over the past 20 years:
https://mollymarieprospect.com/blog/conclusion/
cuzzinjack
