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Identity HelpQuartz or Feldspar?

23rd Oct 2019 00:36 UTCRobert Darabos

Found this earlier today on an outcrop / roadcut outside of Antigua, Guatemala.  
I have not seen anything like this in the area, so grabbed some specimens to take home to test.  

It is both brittle and hard.  It does no appear to scratch from a steel knife.  Some areas either appear to scratch or are just crushed.  The crystals are fairly small so hard to tell.  

Does this appear to be Quartz or Feldspar?  

23rd Oct 2019 00:36 UTCRobert Darabos

a freshly broken surface

23rd Oct 2019 00:42 UTCLouis Zulli

To me, it appears to be mostly feldspar, with some clear quartz and some dark mineral, which at first glance, looks a bit like magnetite. 

The whole rock seems like a coarse syenite.
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