FMF - Friends of Minerals Forum, discussion and message board

[pleiistocene]

I acquired this mineral without any specifications. I need help identifying it!

My guess is that it is Arsenopyrite.

It is black with a metallic lustre, shines blue/purple/green under lighting. The specific gravity is unknown although it is fairly heavy (maybe around 5-6 range). It scratches a knife blade. The specimen is 13cm in length and 9cm at it's widest.

The things that is stumping me is the crystal habit, which I believe isn't common for Arsenopyrite.

[pleiistocene]

Here is another angle.

[kushmeja]

Pretty sure that you have Hematite, in particular bladed Hematite aka Specularite.

[pleiistocene]

Thank you for the quick reply! I did think of that as well, although I know Hematite has a slight magnetism to it but does Specularite usually do too?

This specimen doesn't have any magnetism to it.

[Bob Carnein]

This doesn't look like any arsenopyrite I've seen. Hematite is definitely a possibility. Your best test will be to take a piece of unglazed porcelain (the bottom ring on a teacup or plate or the back of a porcelain tile) and rub the specimen against it. If the mineral is hematite, it will leave a red-brown streak.

If the specimen scratches a knife blade easily, it might also be silicon carbide (carbonundum), which often occurs as iridescent hexagonal plates. It's man-made. Hematite isn't much harder than a knife blade, but remember that knife blades themselves don't all have the same hardness.

[Kevin Conroy]

Could you please post a photo of the back of the specimen, showing any matrix that may be present? A close-up of the front and back may also be helpful in the identification.

[alfredo]

Check whether it easily scratches quartz. I'm thinking synthetic silicon carbide.

[makokerowill]

Pyrrhotite?

[James Catmur]

I tend to agree with Alfredo, until we see if there is any matrix