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.
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?
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.