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Possible pitchblende - any ideas?
  
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Murray




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PostPosted: Apr 16, 2017 04:09    Post subject: Possible pitchblende - any ideas?  

Hi folks.

First time poster and only today did I join this forum.

My son and I were on holidays and did a bit of fossicking as I'm trying to get him interested in my old hobby. We found an unusual rock in central Queensland in a weathered volcanic range (most of Australia's east coast is volcanic in origin).

I had no idea what it may have been and cracked a piece of it with a rock hammer.

Now, I am not a geologist, nor do I consider myself to be an idiot. All I did was that I hit a rock with a hammer...so at worst I could be classified as ignorant. However, having taken some chunks with us, I looked into what it may be and the closest match I could find is pitchblende.

There are no known areas of occurrence of pitchblende or commercially viable bodies of radioactive ores in the area where we found it.

There is a brittle layer on the outside of the samples perhaps 15-20mm thick. It has a dull silvery sheen when broken - see third image. It is heavy, not as heavy as pure lead but heavier than normal rock. I am not going to be touching it (the samples are wrapped up in my shed) until I know more about it. As you can see, I have not cleaned the samples. This was because I came to suspect it may be pitchblende before I got around to cleaning them.

I am hoping to get a sample to a geologist in the next few weeks but in the meantime I would greatly appreciate it if anyone could tell me whether my concerns about this mineral are real or unfounded.

The samples are being stored away from people and pets.

Hope you can help.

Cheers,
Murray.



Pic 2.jpg
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Central Queensland
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Pic 1.jpg
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Central Queensland
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Central Queensland
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alfredo
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PostPosted: Apr 16, 2017 04:44    Post subject: Re: Possible pitchblende - any ideas?  

Welcome to the forum, Murray.

The first thing to do, if you don't know anyone with a geiger counter who could measure the radioactivity directly, is to determine the "streak color" of the black material, ie the color of its fine powder upon crushing a tiny grain, or rubbing it on a piece of unglazed porcelain tile. If the streak color is yellow-brown or red-brown, then you probably have an iron mineral. If the streak is black, then we can recommend further tests of other types.
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Murray




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PostPosted: Apr 16, 2017 04:59    Post subject: Re: Possible pitchblende - any ideas?  

Thank you Alfredo.

I forgot to mention that it was non-magnetic when I ran a neodymium magnet past the samples and got no reaction, even from the fragments.

The soil in the region the samples comes from is orange. There is magnesite in the area. A piece or magnesite I tested with a magnet from near where I collected these specimens was mildly magnetic. The magnet test was why I discounted ferrous metals but I'm very low on experience in this kind of thing.

I don't know anyone with a geiger counter and don't have any kind of network to discuss minerals that isn't 10 years old and is currently trying to resist going to bed by talking my ear off about the novel series he's reading.

The magnet test may be a little simplistic to discount the possibility of ferrous metals. It's night here so I'll consider your suggestion re crushing again in the morning.

Thanks again.

Cheers,
Murray.
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Peter Megaw
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PostPosted: Apr 16, 2017 09:16    Post subject: Re: Possible pitchblende - any ideas?  

Murray, given the botryoidal (bubbly) habit, the volcanic environment, and your mention of red soils and some magnetite (not magnesite) in the area it is probably the common iron mineral hematite. Alfredo's streak test will probably confirm this very quickly.

Even if it does not show the distinctive red brown streak of hematite it is more probably a manganese oxide mineral than pitchblende. Unless you were someplace really remote, the quantity of the black mineral is high enough that were this pitchblende this rock would be seriously radioactive and prospectors probably would have found it years ago. I suspect this would be easily detected by a regional airborne survey were it pitchblende, but you never know.

For you....and other FMF members interested in radioactivity, it is no longer necessary to know a dinosaur who has an old geiger counter stashed away or shell out big bucks for a scintillometer. There is a nifty cell phone geiger counter accessory available on the internet for $35US. it's called "Smart Geiger" and seems to work quite well. I have one and have checked it against a "real" detector and it passed the test. Simple little detector plugs into the microphone hack and the app downloads right to your phone. I have an android but I think it works on an iPhone too.

However, if you're feeling lazy...or cheap...you could just put a chunk of the stuff in your suitcase next time you check on a plane. If it is pitchblende the airport security guys will let you know right away....just make sure to get to the airport 4 to 5 hours before your flight because they won't believe you just stumbled across this in the desert!

Good luck with your fossicking and welcome aboard.

Peter

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Peter Megaw
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PostPosted: Apr 16, 2017 09:21    Post subject: Re: Possible pitchblende - any ideas?  

should have mentioned that hematite is not magnetic ...its made of ferric (+3) versus ferrous (+2) iron.
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markbeckett




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PostPosted: Apr 16, 2017 13:44    Post subject: Re: Possible pitchblende - any ideas?  

Hi Murray - 'Pitchblende' is twice as heavy as any iron oxide, so if you have access to samples of each, you should be able to determine which is (easily) the most dense by handling them. ;-)

Hope this works!

Mark

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Murray




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PostPosted: Apr 16, 2017 20:50    Post subject: Re: Possible pitchblende - any ideas?  

Good morning. Peter's email reminded me that there is an abandoned manganese mine some distance away but in the same geological formation. It never occurred to me that it might be some form of manganese - as I said, I'm new at this.

Some of the images of botryoidal manganese are very similar. Given the known presence of manganese I tried a scratch test. While it's brittle stuff, it's clearly harder than the tile and scratched it. Photo attached.

I also passed a magnet over the dust and a number of tiny fragments were magnetic. Does this mean it's ferrous, as opposed to ferric?

So probably not goethite, ergo it's most likely a ferrous manganese ore?

The landowner would be very happy if it's not radioactive.

Cheers,
Murray.



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Murray




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PostPosted: Apr 17, 2017 04:44    Post subject: Re: Possible pitchblende - any ideas?  

Something in the Psilomelane group perhaps.

Cheers,
Murray.
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Pete Modreski
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PostPosted: Apr 17, 2017 12:16    Post subject: Re: Possible pitchblende - any ideas?  

Murray,

I think you're on the right track, about "something in the psilomelane group". Iron and manganese oxides are both pretty common, and both can form veins and crusts/coatings that look botryoidal. The manganese oxides can very, from quite soft, to quite hard. If the material and the streak are black, you can be quite assured that it is one of the manganese oxides; there's no easy way to tell which exactly among the many, complex manganese oxides, without chemical or other tests. If it looks solid, usually shiny, black, but has a red-brown streak, then it's probably hematite. And if a duller brown to black, with a brown or yellow-brown streak, goethite, of which "liimonite" is the (not a single specific mineral) is the noncrystalline or impure form, usually softer and with a yellow-brown streak.
And the iron and manganese oxides can occurs mixed together too, rather than pure, so that may complicate things.
And a last comment, these "modern" rare-earth magnets are so very strong, that will be able to pick up especially tiny fragments of many minerals that only have a small iron content, and are normally thought of as being non-magnetic, or that only have a small amount of magnetic mineral grains intergrown in them. In fact, one of the traditioinal, old type, less strong magnets is probably a more useful and reliable test than the Nd magnets, because it will just be attracted to the very magnetic minerals (mainly, just magnetite), and "it will ignore the rest". Or best, test with both kinds of magnets.
Best of luck,
Pete (Modreski)
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Josele




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PostPosted: Apr 17, 2017 12:40    Post subject: Re: Possible pitchblende - any ideas?  

Peter Megaw wrote:
should have mentioned that hematite is not magnetic ...its made of ferric (+3) versus ferrous (+2) iron.

Hematite is not magnetic enough to note it with a standard magnet but it sticks to a neodymium magnet.



P1090561.jpg
 Mineral: Hematite
 Locality:
Haramosh Mountains, Skardu District, Baltistan, Gilgit-Baltistan (Northern Areas), Pakistan
 Dimensions: 6 x 4.5 x 1.5 cm
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Neodymium magnet is 6 mm in diameter
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Murray




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PostPosted: Apr 18, 2017 21:42    Post subject: Re: Possible pitchblende - any ideas?  

Many thanks to you all for your assistance.

Cheers,
Murray.
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