Gold and purple?

[Tivru 0]

I stepped on a rock yesterday and picked up something beautiful. Can anyone help me out with this? It's sturdy, dark grey, and has a layer of dull blue material splitting through gold-ish and red-purple reflective patches. Found in Georgia, but in a paved area.. (possibly a lost rock or something someone found and threw out later, I'm not sure)

[Goldfinger 43]

Hi-

My guess is either chalcopyrite or bornite. Both of them can look very similar. But the golden sheen on yours makes me think it's chalcopyrite.

Bornite also has goes by the name "Peacock Ore" although most peacok ore being sold is really chalcopyrite. Go figure. :whaaaa: :spinnin:

http://www.mindat.org/photo-276035.html

http://www.mindat.org/photo-145852.html

You can do a streak test. That may help to indentify. http://www.minerals.net/resource/property/Streak.aspx

You can use the underside of the lid on your toilet tank as a streak plate. Carefully observe the color of the streak.

http://www.minerals.net/Mineral/chalcopyrite.aspx

http://www.minerals.net/Mineral/bornite.aspx

Steve

[Tivru 0]

Hey Steve,

I did the streak check (thanks for the loo tip) and between the two I'd actually want to go with bornite. I saw I dark grey streak without hints of green (hmm, though "slightly green" is a hard distinction off of grey-black..). Moreover, the description of the gold sections as copper-red to yellow-brown echoed my thoughts on first seeing it.

I noticed both minerals should contain iron? I have some finger-breakers laying around (neodymium magnets), and I'm not getting any attraction. Is that to be expected?

Thanks for the input and the nice pics!

[Goldfinger 43]

The iron is in the form of sulphides which makes it non magnetic.

Steve

[Tivru 0]

Interesting, the electrons pair up. Well, thanks again : )

[Goldfinger 43]

Interesting, the electrons pair up. Well, thanks again : )

By the way- the streak plate is supposed to be white unglazed tile and you can use the undersides of the lid on the toilet tank assuming that's what color it is. It might also be tan from long use which would throw off any results you get from your test.

If it's not, you can pick up a piece really cheap at a tile store for future testing. Another thing is sometimes it helps to smear the streak with your fingers to spread it out if it's hard to distinguish the color of it. You might be be able to see more green in it if this were done.

Steve

[Tivru 0]

Both of the lid pieces are plastic, I used the side of the tank (I'm pretty sure it's glazed). I'll keep an eye out for a better plate and try to smear it. I just did a tile job for my uncle.. but the underside was a red-brown. I don't know, I find all sorts of scraps on the road, I'll find something.

Quartz is about as interesting it gets around here, but I've yet to find a nice crystal. I do keep an eye out for softer stones that I can polish, like these black rocks

Unfortunately they breaks in layers, so it's a little difficult to get a good cut. : /

[Goldfinger 43]

Looks like what you have is black gneiss. I never would have even thought about trying to polish that, if in fact that's what it is.

Steve

[Tivru 0]

I can't find a similar picture with gneiss. I was thinking it was a type of coal. It's similar to shale and jet, they just don't have the same luster. It's very easy to polish, I'm just using a nail file.

Edit: Anthracite! I think it's anthracite. Colored a harmless blue in the factory! Heheh.

Btw, I know understand which lid you meant, and the results were much better. Dark grey/black, without a doubt.

[Goldfinger 43]

I don't know of any anthracite that peels off in layers like yours. If you think it's a form of coal, put a small piece into a direct heat like a gas burner, electric grill on your stove and it will reduce to ashes.

So it was bornite after all. Nice piece.

Steve

[Tivru 0]

It flares, then smokes, turns red; didn't wait to see if a whole piece ashed (used a lighter). As for the layers, this stuff is brittle and it takes some effort to bust up a larger piece, so it may just be the way I was going at it.

Mystery solved. Thanks man.

[Goldfinger 43]

So it was a piece of coal. I thought is was some type of gneiss or schist just looking at the photos and never even suspected coal at all. But like you said- mystery solved...

Steve