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Specks of white shiny magnetic metal - are they iron, nickel, or chalcopyrite?
  
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GabiG




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PostPosted: Dec 22, 2019 09:04    Post subject: Specks of white shiny magnetic metal - are they iron, nickel, or chalcopyrite?  

Hi all, Could you help me identify the metal in these rocks? The samples contain tiny specks of shiny white metal with a somewhat splattered look. The samples respond to a neodymium magnet, i.e. the magnet wants to attach to the rocks at the point of the white metal specks and the smallest rock can actually be pulled by the magnet. My Garret Pointer is very active towards them. The quantity of metal is unfortunately very small, so a streak test would be very difficult. Most asked so far suggest it's chalcopyrite, but I'm confused about the strong magnetic response. I collected the samples at a disused lead/zinc mine. Thanks.


5.jpg
 Mineral: Pyrite
 Description:
Lead mine, Isle of Man
1mm specks?
Sample of white metal in quartz. Possibly pyrite.
 Viewed:  2236 Time(s)

5.jpg



8.jpg
 Mineral: Pyrite
 Description:
Lead mine, Isle of Man
1mm
Close-up of white metal in quartz. Possibly pyrite.
 Viewed:  2231 Time(s)

8.jpg



4.JPG
 Mineral: Pyrite
 Description:
Lead mine, Isle of Man
Various
Close-up of white metal in quartz. Possibly pyrite.
 Viewed:  2233 Time(s)

4.JPG



1.JPG
 Mineral: Quartz with metal
 Description:
Lead mine, Isle of Man
various
Quartz samples from a lead mine containing small quantity of white metal. Possibly pyrite.
 Viewed:  2234 Time(s)

1.JPG


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Matt_Zukowski
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PostPosted: Dec 22, 2019 10:13    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Can you find the locality in mindat?
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GabiG




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PostPosted: Dec 22, 2019 10:53    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Yes, the locality on Mindat is Isle of Man - 72
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Bob Carnein




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PostPosted: Dec 22, 2019 10:58    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

It looks to me like pyrite. Try the streak (black, possibly with a greenish tint, if it's pyrite); try the hardness (close to that of a knife blade; it will scratch steel if the test is done carefully).
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GabiG




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PostPosted: Dec 22, 2019 11:09    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Isle of Man near the Snaefell/Laxey Mine
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Bob Carnein




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PostPosted: Dec 22, 2019 11:10    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Sorry, I didn't read the original post carefully; pyrite isn't magnetic (nor is chalcopyrite). Pyrrhotite is somewhat magnetic; color and lower hardness also help to distinguish it from pyrite (pyrrhotite usually has a bronze tint, which I don't see in the photos, and it's softer than steel). Can you try scratching your sample with a needle? You can try the streak of even a small sample by rubbing it against the white ring on the bottom of a porcelain teacup or saucer. Are you certain that there isn't another mineral present that accounts for the magnetism?
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GabiG




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PostPosted: Dec 22, 2019 11:21    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

I'll have a go at what you suggest. Will try later as going to work now! :-( I will also try breaking one of the rocks further to see if any other metal is present. Thanks very much!!
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Pete Richards
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PostPosted: Dec 22, 2019 13:51    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Mindat's list of minerals for the Laxey mine mostly contains sulfides, including pyrrhotite. Magnetite seems unlikely in this setting, I vote for pyrrhotite (tentatively). My reasoning, of course, assumes that the Laxey mine geology is similar to the place you collected.

Magnetite should be much more strongly attracted by a magnet than pyrrhotite - you might try an old-fashioned "ordinary" iron magnet for perspective.

If you break up one of your lumps, you may well release some isolated fragments of your mystery mineral, which should be easier to work with.

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Joseph DOliveira




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PostPosted: Dec 22, 2019 16:38    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Hexagonal pyrrhotite is not magnetic but monoclinic pyrrhotite can be quite magnetic.
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GabiG




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PostPosted: Dec 23, 2019 06:18    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Oh! :-D That sounds confusing! Not sure how to tell the difference with the small sample size I have :-/ But I'll continue to investigate to still my curiosity :-D Thank you :-)
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GabiG




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PostPosted: Dec 23, 2019 07:58    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

I tried the magnet test, and you are right. The Ferrite magnet doesn't have any effect on the small rock. The Neodymium of course pulls it straight away. I can't test the other rocks because they are too heavy. I need to break them up first. The sample comes from near the North Laxey Mine. It's a lead mine but apparently a little galena was discovered there also and pyrites and zinc of course. I will try and isolate some of the metal :-) Thank you :-)
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PostPosted: Dec 23, 2019 08:45    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

I tried scratching some of the specks with a needle. Difficult because they are so small. They seem hard and a tiny fragment of quartz came off with a metal speck left on it. It literally flew towards the magnet as soon as I put it near it. Actually, it was drawn by both magnets - ferrite and neodymium. I haven't been successful with the streak test yet, but I keep trying. Will also try to break some rock a bit more to see if other metals are present. The mine did have a small amount of galena apparently, but isn't that black?
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PostPosted: Dec 23, 2019 12:20    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Galena is silvery grey in color, not black.
The magnetic material sounds like pyrrhotite, as others have pointed out. And both pyrrhotite and galena will react to electronic metal detectors. Pyrrhotite, galena, covellite, and graphite are the four minerals that frequently give "false alarms" (or "false excitement"?) to a friend of mine who detects professionally for gold.
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PostPosted: Dec 23, 2019 13:25    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Well, taking all the information into consideration, I think it must either be pyrrhotite or galena :-) I will try and collect sufficient of the material to do a streak test. But I wonder if they would both have similar streak colour? Anyway, it's worth a try and all good for learning! :-D
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Bob Carnein




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PostPosted: Dec 23, 2019 13:39    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Once again, you need to try scratching the mineral with a pin or needle, or try scratching a steel knife blade with it. (Be careful you aren't simply crushing the mineral--try both the needle on the mineral and the mineral on the knife blade.) It it's harder than steel, it isn't galena, pyrrhotite, or chalcopyrite. It appears to have a conchoidal fracture, which would rule out galena. Streak isn't going to help you much to distinguish between these and pyrite. You also should crush up a sample and see whether you can separate out the mineral you're trying to ID; then try the tests on it (including magnetism, using an "ordinary" magnet).
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Pete Richards
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PostPosted: Dec 23, 2019 16:29    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Bob Carnein wrote:
(snip) It appears to have a conchoidal fracture, which would rule out galena.


In fact, galena has perfect cleavage in three directions, like salt. Any loose particles of your mineral should look like little blocks with all right angles if it's galena.

And galena is not attracted to a magnet....

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PostPosted: Dec 24, 2019 05:01    Post subject: Re: Specs of white shiny magnetic metal - are they iron, nickel or chalcopyrite?  

Thank you again! :-) You give me so much information. I'm very grateful! I am going to crush one of the smaller rocks and try separate all the metal elements as best I can. Then I will try what you suggest.
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PostPosted: Dec 25, 2019 09:13    Post subject: Re: Specks of white shiny magnetic metal - are they iron, nickel, or chalcopyrite?  

I have now tried the scratch test against a stainless steel knife. Some isolated mineral crumbs from the rock sample did not scratch the knife surface when I rubbed them against the knife surface. In fact, they crumbled to almost a powder. Scratching one of the fragments with a needle caused some bits to come off the fragment. So, it’s possible to scratch this mineral with a needle. I also tried the streak test. The streak is dark grey with no hint of green. I took some more close-ups of the mineral fragments and I cannot see right angles. But the rock crushed well, so maybe the mineral fragments were also crushed too small. Anyhow, there were a couple of slightly larger ones to photograph. The magnet test showed that the fragments attached easily to even a weak fridge magnet. I think it’s ferrite but not absolutely sure. So, does that make it pyrrhotite?


Fragment 1a.jpg
 Mineral: Pyrrhotite?
 Locality:
North Laxey Mine area, Laxey, Isle of Man
 Dimensions: 2mm
 Description:
Photo 1 of isolated Fragment 1
 Viewed:  1666 Time(s)

Fragment 1a.jpg



Fragment 1b.jpg
 Mineral: Pyrrhotite
 Locality:
North Laxey Mine area, Laxey, Isle of Man
 Dimensions: 1mm
 Description:
Photo 2 of isolated Fragment 1
 Viewed:  1666 Time(s)

Fragment 1b.jpg



Fragment 2.jpg
 Mineral: Pyrrhotite
 Locality:
North Laxey Mine area, Laxey, Isle of Man
 Dimensions: 1-2mm
 Description:
Isolated Fragment 2
 Viewed:  1668 Time(s)

Fragment 2.jpg



Fragments a .jpg
 Mineral: Pyrrhotite
 Locality:
North Laxey Mine area, Laxey, Isle of Man
 Dimensions: 1-2mm
 Description:
Mineral fragments together
 Viewed:  1667 Time(s)

Fragments a .jpg



Fragments b.jpg
 Mineral: Pyrrhotite
 Locality:
North Laxey Mine area, Laxey, Isle of Man
 Dimensions: 1-2mm
 Description:
Photo 2 of fragments together
 Viewed:  1668 Time(s)

Fragments b.jpg



Fragments crushed.jpg
 Mineral: Pyrrhotite
 Locality:
North Laxey Mine area, Laxey, Isle of Man
 Dimensions: -1mm
 Description:
Example of crushed rock with mineral fragments
 Viewed:  1666 Time(s)

Fragments crushed.jpg


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Bob Carnein




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PostPosted: Dec 25, 2019 11:17    Post subject: Re: Specks of white shiny magnetic metal - are they iron, nickel, or chalcopyrite?  

Sounds like pyrrhotite to me. Mindat includes it in their list.
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