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Rick N

March Issue Of Icmj

59 posts in this topic

Excellent article Ralph.

 

I really enjoyed reading it and have a thirst for more.

 

I have been exposing a quarz reef by hand specifically for viewing the different sections / layers and trying to understand what I am looking at. It is a 1850's surface pocket mine. Your article put more into focus than I have been able to obtain reading and view videos online.

 

Now if I can just put a name to the individual rocks / material I am looking at I can speak the language somewhat better when describing my situation.

 

post-25522-0-81080400-1425322641.jpg

Yellow lines follow the strike, shovel is leaning against the reef, 45° dip. Gossan(?) surrounds the quartz top and bottom.

 

Do you have any idea what would cause the structure at the top of the image? Crumbly type material. Still mucking out the hole, deepest point below the detector is still dirt going down. Haven't reattached to the vein material yet down there.

 

I plan on writing a story of what I find as I uncover this 49'ers diggings. No trash, just boot tacks and a horseshoe. Exposed vein material is how it was left. The hole had been caved / filled.

 

Plan on making this a wine cave.

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I write lots of articles, so I am not really sure which one you are referring to, but I am glad you enjoyed it.

No, you cant tell from just looking at a specimen if its taken from the hanging wall, foot wall or center.

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Technical I like, especially when it comes to staring at a rock face and trying to determine, left, right, up, down? Gravity doesn't always play a part I am learning.

 

Quick question, in the image above, does the structure in the top left corner look like some kind of bubble or lens effect? Very crumbly and layered.

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Rick,

 

Geologists are observers just like you.

 

If it's on top - it's probably younger rock. If it's crumbly - they call it crumbly. Pale green is called "pale green".

 

Rocks have names. Ryolite, Granite, monzonite. Biotite, lepidolite, hemimorphite magnetite - it's a long list.

 

You may name the rocks with reasonable certainty upon field visual inspection. You can name them more precisely with assistance of microscopic inspection. Further identification is possible at additional cost involving a nearby university geosciences lab.

 

What is the host rock?

 

What is the deposit model? Was it intrusion related? Was it epithermal? Was it volcanogenic? Sedimentary?

 

Structure is important. Is it a fault? Which rocks went in which direction? Up? Down? Left? Right? How far? What is the dip? What is the strike? Is it a low angle fault or a high angle fault? Is it parallel, sub parallel or a cross fault? Are there other nearby faults?

 

What color is the host rock? How old is it? What is the mineralization? What are the types of crystallization?

 

Where did the rocks come from? When did they move here? What moved them? What forces acted upon these rocks?  

 

What was the sequence of events? Minaralization can happen at different periods of geologic time. Was faulting pre mineralization or post mineralization?

 

It's an interesting hole. :)

 

- Geowizard

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post-13168-0-99177700-1428512828.jpg

Geo,

 

 

What is the host rock? Was it a monzonite intrusion? Was it epithermal?

Mesothermal, Orogenic intrusion zone.

Structure is important. Is it a fault?

Yes

Which rocks went in which direction?

 

Up? Down? Left? Right? How far? What is the dip? What is the strike?

It is a reverse fault system, strike is NE at about 8° with a dip of 45°.

 

What color is the host rock? How old is it? What is the mineralization? What are the types of crystallization?

Host rock is greenstone. Quartz reef with calcopryite and iron pyrite, calcite, serpentine. Center of quartz is white with disrupted zones on both sides of red/orange slate type material that I have not id'd yet.  This material has small quartz rocks throughout with free gold in the minus 100 mesh size. We are 1.5 miles from Coloma and sitting on the Mother Lode vein system. I have identified two separate reefs next to each other. Both showing good color in the tailing piles. Heavy staining. Original "pocket mine" typical for this area. I mucked out the small depressions to find where the original miner stopped mining. This is what you see above. 

 

Where did the rocks come from?

Melones Fault System

 

 

 

It's a hole. :)

 

- Geowizard

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I'll just bust open that one rock to the left of my detector in the image and see what's inside. That and continue to follow the edge of the strike that the old timer was following down.

 

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Technical I like......
sitting on the Mother Lode vein system.....
Melones Fault System....

Hi Rick -

It just happens that up and coming in this next month's issue (May) is a technical article on the quartz veins of the Mother lode system, including why the melones fault system is so closely associated, what the melones fault represents, why serpentine is so common, how the gold is deposited, etc.

It wont be a map of where to dig in your prospect, but may explain in a larger view why its there.

Although substantially complete, the article is actually still being written - any particular thing you'd be interested in seeing me cover?

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Your last article read to me like a road map. Looking at the rocks and layers, I can see the actions you mention.

 

What indicators would someone look for when looking for enrichment zones? I've been watching Prospectors and they keep chasing Pegmatites to locate gems, is there something in a quartz vein system that has the same indicators beside iron staining?

 

One question would be where did the mud stone come into play? I have a large strike of what I have been told is mud stone, loaded with pyrite, hitting the quartz vein at an angle, this is where one of the original miners took out some nice gold. Is this just another fracture in the evolution of the vein system? It looks like it came in after the quartz.

 

I would like to know more about the different minerals involved, how to identify them and how they related to the gold formation.

The layers are gossan down to near the quartz, then gray clay, then the vein. Should I sample the clay?

 

I have talc, grey clay, dark blobs of blackish mud that is mineral rich and the GB 2 sounds off on them. The red/orange material surrounding the vein, hard with frontal impact but flakes off in large flats when hit from the side. Loaded with very small quartz fragments and free gold in very tiny sizes.

 

Quartz has instances of serpentine on it, and voids with very red dirt inside as well. 

 

I am on part of the system that doesn't have the Mariposa slate, greenstone is the host rock striking mostly true north. 

 

I'm thinking this may be the location of Kanaka Jack's diggings that were never found, that and his stash.

 

Very little trash, no signs of a miner working these pockets. Just a button and a horseshoe that was left buried 3 feet down against the face of the vein covering a nice vug of gold the old timer left for me. Haven't found a camp, nails or nothing about where this miner was staying while working these diggins. He must have came in every day and then left at the end of the day. Had a donkey as I found a shoe. He also wore an old military style coat, found a button off of that.

 

If you need some surface pictures of quartz reef material, I have two locations that have the vein system exposed.

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Rick,

 

What was in the rock?

 

If the answer is; "I don't know, Geowizard",,,

 

Then... get a big hammer and "whack it"! :)

 

Crush it, screen it, pan it.

 

"It's an interesting hole."

 

- Geowizard

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Rick,

 

While you're in the mood,

 

Knock off a chunk of the other two bad boys and run them through the crush screen and pan process.

 

You MAY have your host rock right there in sight!

 

You should be certain what the host rock is!

 

When you have identified the host rock, we will give it a name...

 

- Geowizard

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Gossans, and many of the red blobs of earthy material in the quartz are remnants of pyrite that has been oxidized and converted by oxygen and rainwaters.

 

In the article, I'll talk about the factors (including iron) that lead to the localization of gold within the vein.

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Excellent. I will reread the article again today and generate some questions I may have. Looking forward to reading the next one.

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Chris, believe it or not, a ML, Garrett and other PI's have to almost touch that rock to get a signal. I figured it to have at least 1.5 oz AU in it.

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Rick,

 

I can believe it.

 

PI detectors are great for nuggets and relic hunting. Your PI detector would easily find a horseshoe or mule shoe.

 

Disseminated gold and sulfides represent difficult targets and are more difficult to detect in mineralized soil.

 

The only way to know is to crush, screen and pan the rock. Have the pan concentrate fire assayed or refined.

 

- Geowizard

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