Is it copper? Silver & copper? Neither?

[stdenis_jd]

Asking for a friend who I usually help ID minerals for, came from the NW lower peninsula of Michigan (U.S.A) more than likely transported via glacier from western UP of MI or north of there.

When she sent me pics, I first thought pyrite in granite but it's definitely not granite and very unlikely pyrite - the color of the flakes is too bronze for pyrite. One of the pics is a close up of the silver area. Looks like there are tiny sections of mica but outside of that I'm stumped. If I had to guess it would be copper ore with possibly silver and some mica.

Completely unsure if mica is known to exist with these metals either though. Haven't done a streak or hardness test yet, just wondering if anyone can ID this off first glance or not. If not, I'll run the tests and see how they streak.

Oh forgot to mention, apparently she cleaned this rock and there was chalcopyrite type oxidation, mostly purple, which after she told me that backed up the copper theory.

 

Amazon Forum Fav 👍

Diving for Pleasure and Treasure - Grab it through Amazon!

[Eu_citzen]

Looks kinda like mica schist with garnets.

 

[stdenis_jd]

Looks kinda like mica schist with garnets.

exactly what I thought when she sent me the pics until I got it in person - she thought it was pyrite which I agreed with but then was thinking schist because of the patterns, but the patterns don't look wavy in person, just layered. It's really strange, but doesn't look much like schist in person even though it does in the photos...the areas that look like garnets (funny you said that, that's what I said too was that there "might be gurnetsindat" haha) are where the copper appears to be. Shiny, slightly more bronze than pyrite (doesn't have a yellow or gray look to it at all) and apparently had a purple oxidation on just those areas that cleaned off easily with a mild dish soap and toothbrush.

The entire rock is shiny, some areas more than others. The silver is on the duller side, the copper is very shiny, and the host rock is somewhere in between. I think I'm gonna take it home, do some tests and take better photos

 

[Eu_citzen]

Compare with phyllite then. But I'm sticking with the mica schist guess. Some alteration (heat and/or preassure) might distort the "looks".

 

[stdenis_jd]

Phyllite, with the sheen, makes a lot of sense...so does schist of course.

Silver colored hardness: 2-2.5
Brown host rock: 4
Copper/brown areas: 3-3.5

Brown/copper areas streaked the same color, the gray area streaked gray/white, host rock streaked rusty brown.

A few more close ups: