How Nuggets Come to Be ...

[nuggethunting]

Hello All,

Many people don't understand where nuggets really come from. There is no doubt for the most part they are formed within Hydrothermal solutions (most of the time quartz). Pictured below is a specimen I found several years ago, but was only 1/2 of the total piece. I actually found both pieces, but they were broken apart. Total weight of each piece was right at 4.5 ounces each, total weight just over 9 ounces.

You can see a gold nugget just about ready to break away from the quartz. Once this piece breaks away it will offically be a gold nugget. Kind of gives you an idea of how pocket type gold-quartz veins form majority of the gold nuggets we are finding today.

Just thought you would enjoy.

Rob Allison

[IronMike]

Very COOL Rob. Is the nugget is smooth? I was under the impression that smooth nuggets were water/rock worn. I have found smooth nuggets in pits and cracks of quartz rocks before but figured that they got there either by the river or the river of water the miners supplied.

Take care.

Micheal

[vini]

WIT WAIT I thought there was a nugget fairly that dropped them hither and fro ?

[whats4supper]

a discussion of how gold and other metals migrate from the depth, was written in 1931:

THE MINING JOURNAL

Further Thoughts on Ore Deposition

By CHARLES E. PHOENIX, Mining Engineer, Bellingham, Washington. A discussion of the article by A. R. Fletcher

published in The Mining Journal of December 30, 1930.

The article appearing in The Mining Journal of December 30, 1930, entitled “Where Does the Ore Come From?†brings up a question well worth one’s attention.

Whether the discussions, that are sure to follow will materially alter the views that are held is a question, but it is hoped that it will bring out a number of facts relative to the physical condition of deep deposits, that may prove of value in this discussion, and as Mr. Fletcher states, retard the mystery of ore genesis at least one step.

....Some authorities claim that the metal values are carried by gel—a form of colbid matter—some by a magma, which is about the same thing so far as density and fluidity are concerned. Yet we know that mine waters carry immense and varied quantities of the elements, and many of these waters are acidic and supernormal in temperature, which is a factor in holding the elements in solution.

The faulting and fissuring of an area may be evidenced as having occurred in several stages by the character of the crystals of the block en masse—chemical changes effected by solutions at depth, with the original mass in more or less plastic state; next by intense and deep fissuring to the “matte-magma†and the filling of the fissure with acid dykes and feldspars, and metal-bearing magmas, which differentiate in solidifying; and in other cases, by another series of faultings to “depthâ€, and the deposition of metals by mineral-bearing chemical solution. Alongside these acid dykes we may find one or more of the precious metals in association with other metals, and in association with such elements as sulphur, arsenic, tellurium, etc.

The force of gravity, exerted as pressure by overlaying rock strata, which of itself generates heat; the chemical reactions taking place within that belt termed the lithosphere, together with its slight but nevertheless present wave-like action, are all factors in the manifestation of phenomena of volcanism and earthquakes. Steam is the dynamic factor in all eruptive or explosive phenomena of volcanism, and in some instances, earthquakes.

Water of saturation, that would be steam or vapor at ordinary atmospheric pressure, becomes a potential factor of eruptive magnitude at the comparatively shallow depths in the lithosphere. At much greater depths, it would cease to be an explosive factor, owing to a lower saturation point and increased resistance. Water of crystalization released through intense heat, would become an occluded gas, and would be an eruptive factor.

The fumes of sulphur are the most predominant gas in the volcanic eruptions, and sulphur is the most abundant of the volatile elements found associated with metals in ore bodies. Other substances such as the chlorides of ammonium, iron, calcium, etc., as well as the sublimates of lead, copper, zinc, and other metals, are products of volcanic activities. Again, these elements are found in crystalized form in vein deposits, the results of deposition by magmatic waters.

From the evidence we have, it seems logical that metals, at the depth of the “matte-magma†or reservoir of the metals, though obviously in chemical solution under static conditions, are not in chemical solution during the stage of migration, from the parent magma, to the zone of deposition. At the initial movement toward egress, the explosive energy of the confined gases soon converts them into a state of gaseous solution. But it is evident that they are not deposited in that state.

The gaseous solution must traverse the fractures and faults of the crushed zone, under the impulsion of enormous pressure, until it reaches the zone of cooler rocks, when it becomes a chemical solution, and continues to traverse the metal-bearing zone, cooling and depositing its contents progressively, until the filling is complete.

In connection with this paper, I am going to submit a few observations,

(a) Attention is directed to the Comstock Lode of Nevada. My citation is drawn from memory—as I have no definite information immediately at hand. But this fact is pertinent, and, I deem, sufficient for the purpose. After the mine reached a certain depth, the temperature changes began to increase, out of proportion to the normal rate. When the extreme depth was reached, the heat of the workings was so intense that work of mining had to be carried on in short relays, and under a spray of cold water. Now, and here is a problem for a geological theorum, given the exact ratio of temperature increase for each level and sublevel, to the deepest part of the workings, and the depth at which each observation was taken, plus the changes in character of the gangue and wall rock, and whatever gases were present, and it might be possible to construct a curve of value in indicating an approximate depth to magmatic conditions. The lode is Solfataric in origin.

( On the 81st Level of the Portland Mine, Victor, Colorado, Cripple Creek District, the south end of the Portland Mine is 10 degrees warmer than the north end. Carbon dioxide gas forms a dangerous factor in the work of mining the south end. At the time I was there, it had not been definitely determined whether it escaped from rock as an occluded gas, or escaped from depth through very thin, minute fractures. The water that was pumped from this mine and other deep workings into the long drainage tunnel K, was nearly 70 degrees, Fahrenheit.

© The three true-fissure veins forming the Lode System of Central City, Colorado, have well nigh perfect walls for a depth of 3,000 feet. At a depth of 400 feet, on one of the veins, a careful examination revealed the presence of serpentine. The lode system was not formed by the thrust of an eruptive magma, though it was unquestionably a disrupting factor or aid. The Argo Tunnel, driven to de-water the lode system encountered very acidic waters.

(d) The copper deposits of Red Mountain, Cascade Range, in Chelan County, Washington, consists of a very fine grade of copper-sulphide ore, in a vein nearly 250 feet wide, and over 2,500 feet below the outcrop. The vein is of crushed and faulted granite, with firm and steeply dipping walls. Extensive faulting of a minor nature was encountered before the main vein was reached, and each had copper sulphides. The vein has an iron capping, and is distinctly traceable for a long distance to, and through a mountain range. It would be interesting to follow up the development to that point with a geological study.

(e) The Gold Hill mining property adjoining the Azurite Mining Company in the extreme eastern end of Whatcom County, Washington, furnishes an excellent surface study of extreme faulting and fissuring, and chemical alterations en masse of rock, of the entire area of lode system. It well illustrates statements made in this article.

the full article, posted in Miner interest at Nevada Nugget Hunter site, can be accessed through this link:

http://nevadanuggethunters.myfreeforum.org/ftopic446-40.php

[IronMike]

Thanks Whats4supper! Good reading material.

Micheal

[lon]

hey Rob

that is a nice find that helps show how one part of it comes together and thank you for the info

good luck

LON