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Are these patterns common for pyrite crystals?


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I've researched pyrite and it says that the faces may be striated. I can't find anything that talks about the patterns I'm seeing here, anyone have any ideal as to what these are and are they common?

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2 hours ago, Kurious12 said:

I've researched pyrite and it says that the faces may be striated. I can't find anything that talks about the patterns I'm seeing here, anyone have any ideal as to what these are and are they common?

5.jpg

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Hmm. I'm not a mineralogist but the angles between the crystal faces in your pictures look to me as if they could be marcasite. Marcasite is an alternative crystal structure of the same chemical compound - FeS2 - as pyrite. Here is a picture, in which you can see the angles between crystal faces: https://www.crystalclassics.co.uk/product/marcasite-15660/

The acute angle, < 45 deg, is quite different from pyrite, which generally has a cubic or icosahedral habit, i.e. with angles >/= 90%.

But maybe someone with more knowledge of minerals can comment. @sethoflagos, perhaps? 

 

 

 

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12 hours ago, exchemist said:

But maybe someone with more knowledge of minerals can comment. @sethoflagos, perhaps? 

Not really my field of expertise here!

Not even sure what the question is.

But if the query is the strong zigzag features, my first guess would be crystal twinning.

Iron pyrites (if that's what the samples are) does have an interesting form in the iron cross twin (example below). Erode an oblique cross-section through that and you might find a similar surface. 

Pyrite-254452.jpg

The 'pyritohedra' form can also generate some exotic angles.

pyrite.jpg

 

Edited by sethoflagos
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Both crystals come from the sample in the photos below. When I first came across this stone, I thought that maybe it was sperrylite because of the odd shaped crystals in the matrix but an xrd, Raman and edx analysis all determined that it is indeed pyrite. If you can zoom in, you will notice that all of the crystals appear have different shapes. I was trying to figure out what these patterns were and see if maybe they could help explain anything about the pyrite. The crystals are extremely small, this entire stone is only about 2 inches long so most of the crystals would be measured in millimeters.

7.jpg

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  • 2 weeks later...
On 5/20/2022 at 9:07 PM, Kurious12 said:

Both crystals come from the sample in the photos below. When I first came across this stone, I thought that maybe it was sperrylite because of the odd shaped crystals in the matrix but an xrd, Raman and edx analysis all determined that it is indeed pyrite. If you can zoom in, you will notice that all of the crystals appear have different shapes. I was trying to figure out what these patterns were and see if maybe they could help explain anything about the pyrite. The crystals are extremely small, this entire stone is only about 2 inches long so most of the crystals would be measured in millimeters.

Have a look at https://en.wikipedia.org/wiki/Crystal_growth, particularly the section entitled 'Non-uniform lateral growth'. I believe that will help explain the regular stepped edges you can see.

 

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