FMF - Friends of Minerals Forum, discussion and message board

[levitate]

Hi,

I am having trouble with the identification of this specimen. I found this in an attic so there is no telling where it originated from. It is extremely dense, about the size of a baseball and weighs almost five pounds. I would appreciate any help that you can give.
It has a very weak attraction to a magnet but it is not attracted to any other metals.

[Chris Foltz]

Looks like some type of ore...

[Antonio Alcaide]

Well, the pic is a bit blurry. However I would dare to say it reminds me of goethite pseudomorphs after pyrite (if actually the color is reddish brown). I think I can distinguish the crystals are pyritohedra, a common habit for pyrite. Although in that case, magnetism is not expected.

Regards

[Jordi Fabre]

[levitate]

Thanks for the help, the photo is not over lighted. The color is mostly a highly metallic silver (like aluminum foil) and some areas have slightly duller grayish tones. No reddish brown color in the specimen,

[Herman van Dennebroek]

In my opinion it looks like skutterudite from Morocco.
Color between tin-white and pale lead-gray. Streak: black; Hardness 5.5 - 6; density 6.5
All these properties you can investigate them by yourself. A good mineral handbook helps a lot.
Success

[Pete Modreski]

Dear Levitate,
I think you should also keep in mind the possibility that this could be a partly-crystallized mass of some manmade metal or alloy, and not a natural mineral at all. I have seen such things before--produced, either accidentally or as a stage in some industrial process, by the cooling of molten metal at a refinery--where some crystals have formed on the surface of the mass of metal.

Most silvery-colored minerals, metallic-appearing that this might be, such as skutterudite, cobalt arsenide, CoAs3 or (Co,Ni)As3, are metal arsenides or sulfides and have densities around 6.5 g/cc; whereas metal alloys are going to be even denser and will feel heavier--for example, cobalt, sp. gr. 8.86, nickel, 8.91 (iron itself is 7.87). I realize that without similar-size pieces to compare, it is hard to judge what the approximate specific gravity of such a specimen actually is; but if your specimen seems "really unusually heavy", it could be some metal alloy. A mineral like skutterudite should not be magnetic at all; the metals, nickel and cobalt, should be strongly magnetic; but alloys can be variable.