FMF - Friends of Minerals Forum, discussion and message board

[Pete Richards]

Sliding off topic but... Speaking of interesting experiments, put a piece of bornite in dilute HCl in contact with a piece of iron or steel. You'll find that the iron gets coated with metallic copper.

[Les Presmyk]

I have to ask who out there has the time to experiment with acids and rubbing iron nails across crystals to see if they change color besides Alfredo?

[Pete Richards]

It's not like I go around randomly rubbing nails and HCl on things.... >:^)

I discovered the bornite thing by accident when I was trying to remove malachite from some bornite and did the soaking in an old steel pan.

[alfredo]

Les, It comes from my previous impoverished low-tech lifestyle in 3rd World villages in the 1970s and 80s; no access to XRD or microprobes. But it's amazing how many low-tech identification techniques one can invent in the kitchen after reading a few chemistry textbooks.

[Les Presmyk]

We should probably go back to some of those tests and techniques. I am never surprised by the resourcefulnes of the human spirit or put another way, necessity is the mother of invention.

[Tracy]

I can do a peroxide test, bur for lack of proper equipment/chemicals to do the other diagnostics (when next I see you Alfredo I'll bring it with me), I'm going with the temporary premise that the silver is a coating (which in parts has a rippled appearance under a loupe, like paint) and that beneath the silver is a rough-textured, second red coating - suggesting that the crystal, whatever color it is, is coated with hematite or iron oxides. I don't see any smooth areas (besides the silver ones) to tell me with certainty what the color might be beneath all the coating(s). All the same, as an empirical question, is it theoretically possible to have a wulfenite crystal that is included with hematite? Maybe I'll carefully try to scratch one of the red edges (close to where it contacts the matrix), that might help.

I did test it with a magnet and if the stuff is magnetic, it's only very weakly so.

[Peter Megaw]

Les, given your experiences in Arizona copper mines you should know the old handspecimen trick of putting a couple drops of HCl from your field bottle onto suspected copper-bearing "limonites" and skootching it around with straightpin (knifeblade) to see if copper plates out. fast dirty and very accurate

[Linda St-Cyr]

Alfredo & Pete - thank you for some cool ideas for my science museum! Now I have an excuse to save all those little bits of minerals lying around. (Actually I was already saving them to try the ID by flame method.)

[Tracy]

Peroxide test was negative, and I don't really want to start scraping at it unless I have to...guess I'll have to wait till I can show it to someone...

[David Catalano]

Hello,
There are a few colors of wulfenite found at Tsumeb, however in early mining operations a blue tinged var. of wulfenite was found. It was known to have a metallic luster. Your specimen looks like bicolor wulfenite. It seems to have sections of color. Awesome piece that you have there. Tsumeb is known for amazing, world class mineral semblances.

[Tracy]

Thanks for the info David!

- Tracy

[Matt_Zukowski]

What a great thread! Interesting chemistry - thanks.

[Val]

I thought you might want to see some photos of my blue Wulfenite from Tsumeb. As you can see it looks metallic with a bluish sheen.