teteragonal rock.

Hopefully these pics are better. It is hard to photograph the matrix and get a proper pic. Thanks to all who are helping me. sincerly homer 9tony0 cole golden spike gem and mineral society.

Looks like a pyrite cube, slightly elongated in one axis direction as they often are. Therefore appears tetragonal, but actually cubic. Incipient surface alteration to goethite gives it a brownish colour, but brassy underneath as can be seen where the corner is broken off.

Hi Homer
Clearly a pyrite. Notice at the edge of the cube, the matrix has a thin layer of light material at edge? That is related to the pyrite growth.
I forget the exact process, someone else please fill that in for me?!
That is a classic combination that occurs in schist or phyllite rich matrix. If you chip an edge off the matrix, the fresh broken surface will be a light greyish to grey-greenish color most likely, with sparkly mica bits.
I have specimens identical to this from the NE US(uncertain exactly, as they were purchased from an estate). The matrix and the face of the crystal are weathered/oxidised, hence the limonite brown coating. The long scratch through the cleaved corner shows the color for pyrite nicely though. It can be from a brassy gold to a whitish/greenish metallic color.

Whereabouts did you find yours, (Nearby town/state) ? You said, Golden Spike Gem and Mineral Society of Utah? or Colorado??
CO has plenty locations as mentioned on the first thread by Peter Lyckberg.
Please do reply,
Thanks,
John O.

no need for more posts on this issue - pyrite, pyrite, pyrite...

cheers