valuation of a ore rock platinum group

Nesslilli48

Nesslilli48

Greenie
Mar 17, 2023
14
4
Minnesota
Detector(s) used
Garrett AT Pro
Primary Interest:
Prospecting

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Nesslilli48 said:
Thank you . i will check reed's out . 75 is worth it i am going to try and get the sample from the middle area. i hope its not radioactive

i am in Minnesota this rock and others i have found are from farmers fields. these rocks have been piled up over the years . mostly i find silver ore rocks these rocks were deposited from the glaciers years ago, when i found this one i picked it for its weight to size ratio. it was completely encased in old seabed then i dropped it in a can of muriatic acid which dissolves the old seabed which is comprised of old microscopic seashells and silty sand. so the old uneducated guess slag isn't even close. my rock man says its metamorphic rock . as sedimentary rock replaced with molten what ever he also thought it may be a skarn
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Interesting hunk-o-something. When you hold back useful information in your original post, you don't get to dismiss a thoroughly educated and useful response such as provided by Clay Diggins, a fellow who never wastes his words. I have learned a lot from the guy, and you could too. I wish you luck with your rock hunting.
 

Ditto to Kray's response above.

Have you checked those whatevers with a neodymium magnet? Considering your location iron may be the primary element in them.
 

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arizau said:
Ditto to Kray's response above.

Have you checked those whatevers with a neodymium magnet? Considering your location iron may be the primary element in them.
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yes it is non magnetic
 

the rock is non magnetic. after a few seconds of contact it reacts to hydrogen peroxide by bubbling. does not react to any commercially available acid . does not contain nickel . i cannot think of any other details.
 

Clay Diggins said:
Streak, hardness and specific gravity tests only work on minerals. Those tests will not identify a rock. Clearly, from the assay and the appearance this is a rock - not a mineral. Those tests won't reveal what kind of rock you have.

An XRF only tests the surface of the rock. It might reveal more elements than the fire assay but it won't tell you the composition of the whole rock only the very small surface area tested. The fire assay is the most accurate and reliable way to determine the percentage of precious metals in your sample.

If you want to know what the rock is you will need to study the geology, mineralogy and stratigraphy of the immediate area it was found. That will also give you some clues as to whether the area is worth mining for it's mineral values. One rock doesn't make a mine or and it appears from your assay that it wouldn't be profitable to process that one rock for it's precious metals. You are going to have to find a lot more rocks of equal or greater value to see a profit.

I'm inclined to think this "rock" may be smelter slag. The density, composition and layered appearance do point to a man made object.

Heavy Pans
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You might the depth analysis interesting.
 

Nesslilli48 said:
the rock is non magnetic. after a few seconds of contact it reacts to hydrogen peroxide by bubbling. does not react to any commercially available acid . does not contain nickel . i cannot think of any other details.
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The bubbling may be because it is reacting with silver contained in the rock. Silver acts as a catalyst and causes the release of an oxygen atom from Hydrogen peroxide so it, (H2O2), becomes H2O and O....the bubbles. Actually, some rockets are propelled using this reaction.
 

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pepperj said:
You might the depth analysis interesting.
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Yes I have those charts. As you can see the metals are mostly limited to a few μm depth. I think gold is something like .004 of an inch depth and the platinum group metals are even less depth at full power.

XRF will be much more sensitive to Calcium and can detect that metal up to a Centimeter deep where gold is only detected to 300 microns deep. Lighter more reactive metals like calcium, potassium, magnesium and aluminum fluoresce more than the less reactive precious metals.

To complicate things even more a rock with a high calcium content can help some elements read much higher than if they weren't in a calcium matrix. For those reasons XRF is very useful for quickly and accurately identifying the elemental composition of an object. XRF is not very reliable at all for determining the percentages of elements in non homogenous material - like rocks.

XRF is useful but it's slippery stuff because of the depth limitations. Those depth limitations put severe constraints on sample size. As always the bigger the sample size the more accurate the testing. To learn more about how sample size affects assays of all kinds read up on the nugget effect. It's an issue in any sampling system not just rocks. The smaller the sample size the larger the nugget effect. XRF takes an incredibly small sample.

Skarns that contain platinum group metals are created inside ultramafic rocks. A little study of ultramafic rocks will give you a better idea of why they are composed of the lighter elements. Platinum group metals are not unknown in skarns but they are rare in that environment. Usually skarns have a specific gravity of around 3.5. Platinum group metals are pretty much always alloyed with iron in nature.

Happy Easter everyone. :thumbsup:

Heavy Pans
 

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