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Quartz with striations
  
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Jim Wilkinson




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PostPosted: Jan 29, 2021 22:53    Post subject: Quartz with striations  

I would like to know what causes this on quartz---have not seen this before


brookite (2).jpg
 Mineral: quartz
 Dimensions: 6 x 4 cm
 Description:
striations on crystalline part of specimen
 Viewed:  1374 Time(s)

brookite (2).jpg


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Bob Morgan




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PostPosted: Jan 30, 2021 12:07    Post subject: Re: Quartz with striations  

I'm assuming you are concerned with the darker, striated crystal in the center of the photo. That appears to be a quartz crystal that developed before the lighter surroundings. It appears to have grown from the bottom left toward the upper face at the upper right of the crystal. Regular prism face striations developed along the way as a result of newer rhombohedral face layers - like the last one on the upper right - not completing spread resulting in stepping toward the top. This is common with quartz as it typically grows faster with the more rapid development of rhombohedral layers resulting in more prismatic crystals than outward spread that would make fatter crystals.
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John Betts




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PostPosted: Jan 31, 2021 11:46    Post subject: Re: Quartz with striations  

That pattern also appears in quartz where a mica crystal grew against the quartz and later was removed or dissolved.
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Matt_Zukowski
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PostPosted: Jan 31, 2021 14:48    Post subject: Re: Quartz with striations  

Just curious - why is the picture titled brookite? Is there brookite elsewhere on the specimen? Is what we are looking at brookite?
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Jim Wilkinson




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PostPosted: Jan 31, 2021 16:09    Post subject: Re: Quartz with striations  

there is no brookite--it was labeled incorrectly
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