FMF - Friends of Minerals Forum, discussion and message board

[Mathias]

I got this specimen from somebody who doesn't like colorless minerals, so he gave it to me, aware of my field of interest. He didn't know what it was. He thought it was Sphalerite.

It is clearly a Ferberite crystal, from Panasqueira (because with this piece, other Panasqueira pieces which I bought from him came in the same package).

It also has pyrite on it, siderite, all very typical.

But a rather big area is covered with a globular/spherical mineral.
I think it is Marcasite. Does anybody recognize this?

The entire piece from left to right is 5 cm.

Thank,
Mathias.

[Jordi Fabre]

I would say Pyrite but it could also be Marcasite. As the image has not enough resolution to do it please check yourself with a magnifier glass if you can see small cubes forming the "balls"

[Mathias]

Dear Jordi thanks again,

I made some better pictures, and yes, the spheres have a granular structure which I haven't noticed before, thus must be pyrite. I'll put it under the microscope later, but I think the answer had already been given.

Thanks an best regards,
Mathias.

[Justin Hickok]

Framboidal, correct?

[jorge santos garcia]

I also think it may be pyrite. Even if the spheres have no discernible cubes, there are a few known specimens of globular pyrite from Panasqueira. On the other hand, marcasite does not come in such shape.

Jorge

[Mathias]

As said I took a closer look with my microscope and yes, with a high magnitude I can clearly see very tiny pyrite cubes, of the size of tenths of millimeters. Very small.
It fits the description of the framboidal structure.
Mystery solved!

Thanks,
Mathias