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EducationIrregular lines in pyrite crystal

5th Jun 2018 10:58 UTCTim Saunderson

02663200016015888359387.jpg
Hi, the following pics are of a 0.48mm pyrite crystal with a pair of irregular lines on the upper surface.

My question is "are these irregular lines stacking faults within the crystal or something similar"?

The crystal has fine striations on the surfaces which I guess indicates polysynthetic twinning.

It is embedded in serpentine; the exposed section was embedded in marble.


Regards, Tim

5th Jun 2018 21:40 UTCErik Vercammen Expert

I suppose it is a mosaic structure, like those in crystals of quartz and fluorite.

5th Jun 2018 23:15 UTCAmir C. Akhavan Expert

Buerger, M.J. (1932) The significance of "block structure" in crystals. American Mineralogist: 17, 177-191.

http://www.minsocam.org/ammin/AM17/AM17_177.pdf

6th Jun 2018 14:18 UTCAlfred L. Ostrander

The fine striations are not polysynthetic twinning but the lines formed by alternating growth of the cube and the pyritohedron.

7th Jun 2018 02:43 UTCTim Saunderson

Thanks Amir, there is a lot to absorb but it explains this phenomenon very well.

And thanks Alfred for the explanation regarding the striations. I just found the following website which explains it with a little more detail (nice photo too) Pyrite, striated


Cheer, Tim
 
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