Unknown from Kelly Mine, NM

These are microphotos of some crystals intergrown with rhombohedral calcite crystals from Kelly Mine, Magdalena District, Socorro Co., New Mexico, USA. I have looked through the mineral list for the mine and am not seeing anything I can associate with these. Can anyone offer some help?


There are a number of similar crystals on the piece all of varying size. Here is another showing 2 different views:



and


From the second picture I can tell that it is not completely flat, but somewhat rounded - getting thicker as you get toward the middle.

Any help would be appreciated!

Thanks
Bob

Looks like marcasite to me!

Or perhaps arsenopyrite.

Interesting on the marcasite.



Others have suggested arsenopyrite and brookite. But I see no Ti nor As minerals reported. Since I probably won't be paying for an analysis, maybe marcasite? is the safest identity for now. That is unless someone else comes along with a better thought.

Thanks!!
Bob

This brings up the question of what were the primary sulphides at the Kelly? We don't seem to have any at all listed on Mindat, just secondary stuff, except perhaps the siderite. Did the mining operation not reach below the oxide zone? Or was the entire deposit oxidized?

Arsenopyrite and other sulphides are listed on Mindat at the mining district level, but not for any of the individual mines! (But then again we do warn people that most locality species lists are far from complete.)



Edited 2 time(s). Last edit at 07/29/2012 08:58PM by Alfredo Petrov.

can be chalcopyrite. i think i saw a kind of rainbow iridescence on the crystal but we can also seen this kind of colour on pyrite like we seen on oxydized pyrite sun . but the line we can observed on the crystal make it look like arsenopyrite. hard to say can be pseudomorphing from an other metal+sulphur minerals.

Looks like Marcasite to me as well, has that iridescence commonly found on marcasite and rarely on arsenopyrite.

Very likely Marcasite, see attached photo! (don't pay attention to the Pyrite on it )





Edited 1 time(s). Last edit at 07/31/2012 04:23PM by Harjo Neutkens.

Thanks everyone, I think marcasite wins. Oh and Harjo, kind of hard to ignore that pyrite. Nice!!!

Bob

How sure are you that your specimen is from The Kelly Mine? John S.

I have specimens of galena, pyrite, chalcopyrite and chalcocite, and sphalerite from the Kelly mine so marcasite would be as good a guess as any since your specimen shows typical crystal morphology for that species. Nice micro!
Ron