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Hi Brad… your photos are a bit blurred, but your sample appears to be a “schist”. Schist is a generic term for a foliated metamorphic rock. It displays well-developed foliation (leaves or sheaves of leaves), often through inclusion of mica. It represents the ultimate stage of metamorphism. 

A schist is usually derived from fine-grained sedimentary rock such as shale that has been exposed to some combination of heat / pressure. Individual minerals in schist have grown during metamorphism so that they are easily visible to the naked eye. 

Foliation takes place when pressure squeezes the flat or elongate minerals within a rock so they become aligned. These rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied. Schists are named for their mineral constituents, for example, mica schist is notably rich in mica such as biotite or muscovite. From what I can see, that is what is depicted in your photo. Below I’ve included a close-up depiction of a mica schist so that you can compare your sample to it as a confirmation. Hope this helps.



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I am around 75% certain that Jim Hemmingway  has  correctly  identified your specimen. As he said the photo is fairly blurry so that other 25% lurking in my mind says that this could also be a specimen of one of the Iron/Copper Sulfides like chalcopyrite or bornite. If tiny pieces of the specimen are easily removed by your fingernail and look like tiny thin sheets then it is definitely a phyllite or decomposing muscovite mica schist. If the specimen is harder and more compact with chunky pieces breaking off then my 25% minority guess is probably closer to the correct ID in which case we are looking at a mineral or combination of minerals.

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Oh I quite agree Jeff. Brad’s photos could depict a number of common sulfides / arsenides and there are other possibilities. For example, I have a few ore samples exhibiting native silver ‘horns’ and veinlets protruding from oxidized surface niccolite embedded in a light brown carbonate rock, that look very similar to Brad’s sample. But I seriously doubt this is what Brad has found in his area, as these are quite rare.

We make our best guess based on the info provided and what we think we see in the photo. The one photo appears to depict some foliation, but there’s no way to be certain. This is why I included a schist photo for him to do a comparison. It ensures that he’ll know if his sample is schist or something else. 


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