Black cubic, shiny ?

[shaman15771]

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

 

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[Brian T. Booth]

Sherman,
I can see the rest of the rock, it's a tanish brown. The rock isn't black. Thus that's a black coating on the rock. The coating might be thick, but none the less a coating.

 

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[MartyRocks]

Here in Nevada, as well as many states here in the desert southwest, can have native rocks get this black coating that takes up to 2,000 years to form on the host rock.
For example, here in the Las Vegas area, we have two parks that have sandstone that has the desert varnish on them.
The native Americans would then carve drawings unto these rocks with desert varnish which we call petroglyphs.
If you look up petroglyphs you will see what I'm telling you.

 

[MartyRocks]

Unfortunately, I don't know where these rocks are from as they didn't mention it, but they look like what I have found out here in the desert.

 

[Brian T. Booth]

Marty Rocks,
I researched desert varnish. Desert varnish is manganese Oxide (MnO). I mentioned it on my original message.

 

[shaman15771]

The brown is a coating not the black. I live in southwest Virginia, no desert. Black is not a coating. I suspect brown/tan is calcite.

 

[Brian T. Booth]

Sherman,
I live in North Carolina from Kentucky originally. I'm a huge rockhounder. I find coatings of manganese stained rocks and minerals in every stream I have ever hunted.
Yes! You might be right. It could be tan to brown calcite. I'm not saying it isn't. All I'm saying is that the black substance on the surface is a coating. And that coating is MnO. You can test for calcite by exposing a clean surface, powder just a very small amount and pour some vinegar over it. If it fizzes, then you definitely have calcite.