Black cubic, shiny ?

[shaman15771]

not sure what this one is either. Thanks you all for your help

 

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[DDancer]

Been a while shaman Cant say for certian what you have. About how hard is it and what kind of streak does it have? Might check for magnetism as well.

 

[shaman15771]

Hi DD, been a while been having problems uploading pictures. Looks it might be resolved. Streak is white, deep scratch in glass, no magnetism, steel will give very light scratch, not sure, might be residue from nail.most interesting is form which is very cubic. Also got what might be some sort of carving like a snake made of multicolored quartz. Will try and upload it shortly.

 

[hvacker]

Interesting. I went on a trip Saturday to a mine south of here that mined Psilomelane for the manganese. The overburden
from the mine was rhyolite with the psilomelane appeared painted on the rhyolite not unlike your rocks.
The streak was white to grey.
Not much to look at but I did find some with calcite inclusions that were interesting.

I'll try to post pictures.

One puzzle was I wanted to see what signal I might get on my detector but I got none.
As manganese is between iron and chromium on the PT I thought I should get something. It might be that the
sample was too thin to effect the signal. Can you test your rocks with your Fisher?

 

[Jim in Idaho]

I was thinking rhyolite myself, but not sure.
Jim

 

[shaman15771]

Hi all, can't be rhyolite that's igneous rock, we have metamorphic here. No igneous at all according to usgs.

 

[Jim in Idaho]

I'd like to see a magnified image of the black material.
Jim

 

[shaman15771]

K see if I can. It's very smooth.

 

[Eu_citzen]

Resembles chalcedony. I think this one does, but rhyolite, when metamorphosed can look similar.

 

[shaman15771]

Black chalcedony? Isn't that onyx?

 

[Eu_citzen]

Onyx has a white banding to accompany the black. So it's not onyx, sorry.

 

[shaman15771]

K didn't know chalcedony came in black

 

[DDancer]

Been weathering other projects.... dark chalcedony is as close as I can guess as well. Chalcedony is usually a light material but dependent on what's mixed in can be almost obsidian like. Your samples pretty uniform as well so a type of potch opal is possible to. Being cubit may just be a result of how it fractured out. Apologies for the late reply.

 

[shaman15771]

Thanks DD!

 

[Brian T. Booth]

Looks to be a rock with possible MnO staining. That black coloration isn't incorporated into the the rock it's coating the rock.

 

[SorenCoins]

Did you extract manganese metal from the psilomelane? I liike geochemistry too!

 

[SorenCoins]

My first instinct was basalt, but maybe melanite garnet?

 

[shaman15771]

It's black all the way through, not just surface. We have several like these.

 

[MartyRocks]

I can't tell from the pictures how thick the black layer on the rock is, but is it possible that is desert varnish on it?

 

[Brian T. Booth]

Marty Rocks,
Desert Varnish?