# Rock hunting for ore in Mexico



## Drewbie (Jan 13, 2011)

Hi Guys!

My first post.

I took the family on an adventure recently and we ended up exploring a dry river bed downstream from an abandoned silver mine.

Sample photos to follow - comments appreciated.


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## Drewbie (Jan 13, 2011)

That appears to have worked successfully, here's some more...


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## Harold_V (Jan 13, 2011)

Welcome to the forum. 
Nice looking specimens. Our resident rock authority (Richard36) may be able to give you his opinion on what you've found. 

Harold


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## Drewbie (Jan 13, 2011)

The area these came from appear to have HUGE hematite deposits? The sand in the river has a distinct purple tint, as do all the dirt roads.


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## Drewbie (Jan 13, 2011)

One last photo...

The white area in the top left on this one is actually dark grey and when I broke the rock, that area was perfectly flat and squared off like a set of steps. Very metallic crystal shine.


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## Drewbie (Jan 13, 2011)

Harold_V said:


> Welcome to the forum.
> Nice looking specimens. Our resident rock authority (Richard36) may be able to give you his opinion on what you've found.
> 
> Harold



Thanks for the welcome Harold.

I'm interested to learn what sort of minerals they are. Good for the kids too - trying to tear them away from playstation and tv is hard work!

Cheers,


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## Richard36 (Jan 14, 2011)

Drewbie said:


> Hi Guys!
> 
> My first post.
> 
> ...





Drewbie said:


> The area these came from appear to have HUGE hematite deposits? The sand in the river has a distinct purple tint, as do all the dirt roads.




Hello Drewbie, 

Exceedingly Sweet Photos! Wow!
I have saw plenty of rock photos from forum members, but these have my interest, for sure!
You are in the top three as far as "Good Ore" is concerned.

Straight out the gate, I know this ore contains Iron, Copper, Manganese, and lead, 
and formed in an area of Hydrothermal alteration within a zone of Pyroclastic Volcanic Activity, hence the purple Rhyolitic rock and, and the clay resulting from decomposed Rhyolitic Rock, and/or ash.

These rocks look like they could have came from my preferred area to go prospecting close by here at home, sweet.

This rock in the photo below may well contain Tantalum if it seems like it is way heavy for it's size, as in a high heft. (High Specific Gravity) The Black minerals that form in this type of rock around here is Tantalite, the primary ore of Tantalum.




The Rock in the photo below is almost exactly the same as the ore from a district close by that was the primary Copper and Silver producing region of my area.




Here is a photo of similar ore from that Copper and Silver producing region.
The difference between the two types of ore is that your ore contains far more of the dark gray material, which is Galena, a Lead Sulfide.




The photo below is the "High Grade" Specimen, and I would love to have this particular piece to add to my collection. I would like to have the above specimen containing Galena as well, for that matter. The photo below contains Lead, Antimony, and probably Silver and Gold.




Here is a photo of an outcrop from a mine in Alaska showing the same red powdery material containing Antimony and Gold.



Thanks for the Sweet Photos.
Find the outcrops that these samples came from.
If you are willing, I would truly like to have the above samples to add to my ore collection.

Sincerely, Rick. "The Rock Man".


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## Richard36 (Jan 14, 2011)

The following photos are of Galena, a lead sulfide, and should produce a button of metallic lead if a pea size fragment is crushed, mixed with a little baking soda and heated with a propane torch.

It's dark black enough to possibly contain Jarosite as well, which is a Silver Sulfide.
These samples don't quite look like Hematite, as you suspected, though they do look similar.
Good guess though. 







Nice specimens. 
I'd like to have the one in the top photo for my ore collection.

I hope that This has been helpful.
Questions and comments are welcome and appreciated.

Sincerely, Rick. "The Rock Man".


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## samuel-a (Jan 15, 2011)

Hi Rick

Could you add any comments about the first three pictures Drewbie uploaded ?


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## Drewbie (Jan 15, 2011)

Thanks for the information so far, Rick.

I'll put that specimen aside for you and keep the other half of the rock for myself.  My wife is likely heading to CA or TX soon for a shopping expedition, so I'll get her to ship it from there.

I'm heading into town tomorrow to buy some crucibles, etc, so I can further investigate some of these rocks.

I guessed hematite because when crushed down, the previously dark grey with metallic sheen turned to a reddish dark brown, and the powder and some of the rocks are SLIGHTLY magnetic. I calculated the density at high 3's to low 4's - that's too low for hematite but I thought I'd just messed up my measurements. When I did a 1oz silver dollar, I came up with 11.56 instead of an expected 10.49.

I find this stuff fascinating but boy do I have a lot to learn!


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## Richard36 (Jan 15, 2011)

samuel-a said:


> Hi Rick
> 
> Could you add any comments about the first three pictures Drewbie uploaded ?




Hello samuel-a,

Photos one and three in the first set are mostly quartz admixed with Rhyolite veins, and formed in a region of volcanism associated with mountain building processes. Areas that contain common rocks such as these are always good places to prospect for Hardrock and placer gold. The metals in these rocks are Iron and Manganese.

Photo # 2 is similar to Greenstone, (which is a contact metamorphosed variety of Basalt due to being super heated by intruding magma), but isn't. I am not quite sure what this rock is as of yet, the composition is different from all rocks that I have studied on, but it is common in my area, and does contain Tantalum, which, as far as I know, Greenstone does not contain. Though Greenstone is associated with placer and hardrock deposits of native gold.




Drewbie said:


> Thanks for the information so far, Rick.



You're welcome.



Drewbie said:


> I'll put that specimen aside for you and keep the other half of the rock for myself.  My wife is likely heading to CA or TX soon for a shopping expedition, so I'll get her to ship it from there.



If willing, I would like the samples in the photos below.
If you're willing to mail these samples from where you are currently located, 
I will reimburse you what it cost to mail these samples to me.















Drewbie said:


> I guessed hematite because when crushed down, the previously dark grey with metallic sheen turned to a reddish dark brown, and the powder and some of the rocks are SLIGHTLY magnetic. I calculated the density at high 3's to low 4's - that's too low for hematite but I thought I'd just messed up my measurements. When I did a 1oz silver dollar, I came up with 11.56 instead of an expected 10.49.



If the stuff produced a reddish brown powder when crushed, then the sample crushed did contain some percentage of Hematite. It isn't pure Hematite though, and that is what threw me on my identification of your samples. It happens.

So, now I figure it is some sort of hybrid mineral consisting of Galena and Hematite, 
an interesting mix, and one that I'm unfamiliar with.

Gold and Silver should be associated with any deposits of this material.
I'd be willing to bet on it. Silver content is almost guaranteed to be present due to the lead content from the presence of Galena, and the Hematite presence is indicative of possible gold content.

I hope that this has been helpful.
Questions and comments are welcome and appreciated.

Sincerely, Rick. "The Rock Man".


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## Drewbie (Jan 15, 2011)

Thanks!

I just returned from a chemical hunt. Found a jewelry supply store that had 900ml bottles of nitric acid, sulphuric acid and hydrogen peroxide but with no percentages written on the label. 33 pesos per bottle - US$2.75

Also grabbed 1kg bags of borax, sodium carbonate, sodium nitrate and "altincar" (in rock form - some sort of flux?).

Plus a crucible. I tired to buy some ash cupels for pulling out lead, but they had no idea what they were.

I can take the galena straight to lead using baking soda, or should I roast it first to exchange the sulphate for carbonate and then use borax? I'm more interested in the other metals content, of course


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## Richard36 (Jan 15, 2011)

Drewbie said:


> I can take the galena straight to lead using baking soda, or should I roast it first to exchange the sulphate for carbonate and then use borax? I'm more interested in the other metals content, of course



I hope that you have some sort of a furnace, 
otherwise you will have difficulty completing an assay, if even possible.

If the galena will reduce to lead in a torch flame, and the lead not be brittle, or hard, then I suppose you could cupel a 30 gram button of lead reduced from the galena just to see if it contains any gold. The bead will most likely look silver though due to the fact that galena usually contains a high percentage of silver.

If the galena will reduce to lead in a propane torch flame, then roasting it is not an option to remove the sulfur content, and would require an actual flux formula and the addition of a couple of iron nails to complex off the sulfur to the slag so that the lead produce from the reduction of the galena will not be a brittle mass because of sulfur contamination.

Try to reduce some of the galena in a torch flame and see what happens.
If the lead isn't brittle, it can be cupeled, possibly without issue, unless the lead contains copper, arsenic, antimony, bismuth, selenium, tellurium, or other impurities that will cause the cupel to absorb the gold and silver along with the lead.

I wish you luck.

Sincerely, Rick. "The Rock Man".


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## Drewbie (Jan 17, 2011)

You were right. My LPG torch (big plumber's model) had trouble even melting borax properly.

I'm going to get an improved torch set up, and also try to locate a source for a platinum wire loop so I can do some flame tests.


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## Platdigger (Jan 17, 2011)

If you want to be able to do quick assays with a torch, check this guy out.

http://www.butlerlab.com/


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## Drewbie (Jan 17, 2011)

Thanks.

I found http://www.dmtcalaska.org/exploration/ISU/unit2/u2lesson3.html to be quite interesting.


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## Drewbie (Jan 17, 2011)

I found a lab equipment store close by and bought some stuff off them for future use.

They didn't have any platinum wire loops, only nickel. I bought one. Any good, or too low melt temp?


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## Richard36 (Jan 18, 2011)

Drewbie said:


> I found a lab equipment store close by and bought some stuff off them for future use.
> 
> They didn't have any platinum wire loops, only nickel. I bought one. Any good, or too low melt temp?



Nickel might work, though I do have some concern.
Any ore with copper will cause you to have to sand the wire after testing in order to remove the copper plating. Aside from that, I suppose they might be ok. The borax used in bead tests might dissolve some of the nickel into it, and cause interference colors, and confuse you on your results, so that is something to test for by creating a bead of borax and looking to see if any color is imparted to it.

Sincerely, Rick. "The Rock Man".


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## Drewbie (Jan 22, 2011)

OK. Starting to get my assaying lab up and running. 

Currently using a bunsen burner running propane.

I tried the borax bead with the loop - I think it's nichrome wire. It gave a slight cyan tinge to the bead.

I think I'll make up my own platinum wire loop. You can buy them, but the ones I found were for inoculting bilogical samples - they're precision made to pick up an exact amount of material. I don't think I need exact amounts for this so a home made job will be fine.

I can buy 26 gauge 90% platinum 10% iridium wire here (used for jewelry welders).

Rick, what's the gauge and loop size of your loop please?


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## Richard36 (Jan 22, 2011)

Drewbie said:


> Rick, what's the gauge and loop size of your loop please?



Hello Drewbie,

I'm not sure of the gauge, the same size as the wire from in a bread sack tie.

That being said, bread sack ties do work, 
though the iron can cause an interference color in the bead.

In a pinch, trash bag twist ties work for your own tests too.
Just tossing ideas out there. I used them for my own tests many times.
The iron, and/or zinc coating will give you issues though.

Fine gauge though, less heat is required to melt the flux.
The larger the diameter of the wire, the more heat it will rob from your molten bead,
thereby requiring a hotter flame source.

I hope that this has been helpful.

Sincerely, Rick. "The Rock Man".


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## Drewbie (Jan 29, 2011)

Well, I'm still hunting down some platinum wire, and building out my chemical assay lab.

In the meantime, here are some close-up photo's of Rick's favourite rock...


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## Drewbie (Jan 29, 2011)

last one...


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## Richard36 (Jan 29, 2011)

Drewbie said:


> ... here are some close-up photo's of Rick's favourite rock...




Yup, these two rocks are my favorite's of the photo's that you posted.







The photo's that you just posted are really nice too.

May I copy and use your photos on my website as examples 
of what to look for when out prospecting?

Sincerely, Rick. "The Rock Man".


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## g_axelsson (Feb 17, 2014)

Richard36 said:


> It's dark black enough to possibly contain Jarosite as well, which is a Silver Sulfide.


Jarosite isn't a silver sulphide, it is a weathering product that contains potassium, iron, sulphate and hydroxide, KFe3+3(SO4)2(OH)6

http://www.mindat.org/min-2078.html

Göran


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## Richard36 (Apr 1, 2014)

g_axelsson said:


> Richard36 said:
> 
> 
> > It's dark black enough to possibly contain Jarosite as well, which is a Silver Sulfide.
> ...




So I got ahead of myself in my thoughts ... Jarsite often contains silver as an accessory metal much the same way arseno-pyrite and chalcopyrite often contain micron gold and silver within the crystal lattice of the mineral.


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## necromancer (Apr 1, 2014)

Drewbie said:


> Well, I'm still hunting down some platinum wire, and building out my chemical assay lab.
> 
> In the meantime, here are some close-up photo's of Rick's favourite rock...




put a ad in the wanted section, you will find your platinum wire,


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