Need some help friends, one of ya know i am sure

[loco oro]

I would like to know what, and what process in the formation of mica,causes this feature I discovered while splitting a large biotite mica (book) this is a sample from a friends property in north Carolina, a historic gold mine, props to friend and fellow tnetter (Buckshot)I collected this sample while visiting and exploring his property, a great experience, back to the mica,I have never found any patterns like this in mica,I immediately thought pyrite replaced by mica, I need your assistance, just want to understand at what point this takes place,and what it was if it is a replacement

 

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[loco oro]

 

[loco oro]

I feel I should say that the (triangle's) are opposite sides of the same feature, one on the left is recessed and the right side is a relief of the same,

 

[smokeythecat]

It is possible there are/were crystals of rutile with it. Rutile is an ore of titanium and occurs frequently in NC.

 

[Clay Diggins]

Good call on the Rutile cat.

Probably not Rutile crystals themselves due to the crystal angles being wrong. They could be impressions of Sagenite crystal forms where they cross. Sagenite is Rutile but the form it takes is due to multiple crystals twinning habit instead of strict crystal form. That would explain the positive/negative impression.

In any case it appears to be a psuedomorph rather than a mica habit. Curiously I've collected some very similar Biotite near Ancho, New Mexico. There is no rutile found in that area. Being a solid solution a lot of Biotite is the result of decomposition of other mineral deposits so psuedomorphs are more the rule than the exception.

Nice interesting specimen.

 

[loco oro]

Thanks for the fantastic info, that's exactly what I wanted to learn, thanks smoky, clay, not often I don't have a clue, needed xperts! ! Very cool