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Author Topic: Help Identifying Mineral  (Read 3742 times)

Offline dgb21

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Help Identifying Mineral
« on: 02/05/2010 06:52:04 »
I found this site while looking to identify a mineral I found some time ago. To say I am an amateur in geology, is an overstatement. Anyways, I found this mineral, I believe while hiking in Connecticut. I have looked through several sites and can't seem to find a definite match. I even bought a couple of field guides with no luck. The streak (see pictures) is brown. It's nonmagnetic. And I would say the luster is metallic. I did a search on this site: newbielink:http://webmineral.com [nonactive]. And the best I could come up with was Aurorite, basically through this image ( newbielink:http://www.mindat.org/photo-190743.html [nonactive]). When I first saw it in my collection again, my first thought was mica, but I thought I would be able to pull off a few mica scales. Lastly, I couldn't find anything to support that Aurorite was found in Connecticut. Thanks for your help and feedback...this is a great site.

Dennis





 

Offline Geezer

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« Reply #1 on: 02/05/2010 08:25:21 »
It's obviously a lump of coal.

No doubt a bunch of sentimental old sedimentologists (like JimBob for example) will try to persuade you otherwise.
 

Offline JimBob

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« Reply #2 on: 02/05/2010 23:15:06 »
It's obviously a lump of coal.

No doubt a bunch of sentimental old sedimentologists (like JimBob for example) will try to persuade you otherwise.

First, Welcome to the site! Then ...

well, you have heard from one of the Seven Dwarfs - Dopey - dgb21. Don't think poorly of use in spite of him.

And Grumpy, er Dopey, both anthracite and bituminous coal have a black streak. Lignite .. eh, yeh, it is sometimes brown, but then it does not look like the picture above, either.

So to property identify this we need a bit more information. Can it be scratched with a knife? Or does it scratch glass?  What was  found with it? Was it taken from a layer of rocks similar or dissimilar to it? In other words, was the rock found in place?

These and probably more questions will help identify this.

Again, thanks for posting!


 

Offline frethack

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« Reply #3 on: 03/05/2010 14:39:54 »
Is the surface somewhat irridescent?  The cleavage makes me think feldspar, and the second picture makes me think labradorite.
 

Offline dgb21

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« Reply #4 on: 03/05/2010 15:43:51 »
Thanks everyone for your responses.

I initially tried to identify this rock by some of the other rocks I normally find while hiking and by what is found in my area. I find a good deal of quartz and barite. There is a barite mine close by. So I started with a internet search of some of the minerals found in CT. Initially, after my search with the streak and hardness, that got me to Wurtzite or Sphalerite (not really sure with the streak). I abandoned those since I have been trying to rely on pictures for a positive identification and couldn't find a match. All that aside here is more information:

- I could not scratch the rock with a penny and it does not scratch glass, but I was easily able to scratch it with my pocket knife.

- I remember finding it pretty much alone just off the beating path where it looked like rain had recently washed out a pretty long area of dirt. I don't really remember picking up anything else when I found it. This one stood out to me and was definitely not found in place.

- It is very reflective when angled right with a light source.

- When I look at it with a hand lens, it is somewhat iridescent in a couple of small areas. But not to the naked eye, like this pic: newbielink:http://en.wikipedia.org/wiki/File:LabradoriteOslo.jpg [nonactive].

I would be really surprised if it was coal. I am not aware of there being many coal deposits in CT, but maybe it was discarded. Or perhaps this accidentally made it's way into my rock collection one Christmas, during my naughty years.

Thank you all again with your help, this is an awesome forum.
 

Offline Bass

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« Reply #5 on: 03/05/2010 19:07:51 »
Welcome to the forum dgb!

My first impression, like yours, is sphalerite (ZnS).  The resinous color, hardness, streak and perfect cleavage all support sphalerite.  Plus sphalerite is commonly associated with barite.  Are there any other old mines in the area?  Any galena?
 

Offline dgb21

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« Reply #6 on: 03/05/2010 21:12:23 »
Thanks much Bass! The only other mines I know of are from this list for Cheshire:

newbielink:http://www.mindat.org/loc-23323.html [nonactive]

I am not sure if that list is complete. I am not aware or have seen a reference to galena mines in this area. I have only been to Roaring Brook and never could find a mine. I have never found Datolite but really I don't know where to look. The Jinny Hill Barite mines are old (1800s, I believe) and I hear they have been a problem since they were never filled in properly. Some properties in the area produce sink holes because of them. But I find the quartz and barite in many areas where there is hiking. There is a pegmatite mines relatively close, in a town or two over also.

Thank you for your response.
 

Offline Bass

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« Reply #7 on: 04/05/2010 03:00:05 »
When I opened you post I thought, "Wow, sphalerite"

Lead-Zinc veins are commonly associated with barite.  Probably closely associated with Triassic extensional tectonics.
 

Offline dgb21

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« Reply #8 on: 04/05/2010 03:32:28 »
Great Bass...thanks much for the info. Best to all that helped.
 

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Help Identifying Mineral
« Reply #8 on: 04/05/2010 03:32:28 »

 

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