Author Topic: Feldspar, really dumb question  (Read 56 times)

dereckc

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Feldspar, really dumb question
« on: July 13, 2018, 12:51:09 PM »
OK forgive me being a newb asking possible a really dumb question about White Feldspar. I was asking in this thread http://rockhoundstation1.net/forum/index.php?topic=3349.0  how to spot areas where to dig for crystals in the Rockies Pike Peak area. Got a few words I did not fully understand Vags and White Feldspar. Looked them up and Feldspar left me with a question. Is White Feldspar the same thing I call an ordinary Quartz Rock I have pictured below? I think so, just did not know it was called Feldspar. Sort of like a Vag is a hole or cavity in a rock.

THX


Oxenkiller

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Re: Feldspar, really dumb question
« Reply #1 on: July 13, 2018, 01:09:55 PM »
No.  Quartz and Feldspar are two different minerals.  The composition is different for one; Quartz is nearly pure silicon dioxide (with other minor impurities to give it opaqueness and/or color) while feldspar is either calcium or sodium aluminum silicate, or "K-Spar," which is potassium aluminum silicate.  It has a lot of aluminum in it- that's the key.  Anyway, It is nearly always opaque (although there are very rare exceptions like sunstones that are transparent) and it will usually be either cream-colored white or off-white (sometimes pale yellowish or pinkish.) It typically isn't as lusterous or glassy looking as quartz, but will form in granite rocks along with quartz. 

That is quartz you have there in the picture above.

dereckc

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Re: Feldspar, really dumb question
« Reply #2 on: July 13, 2018, 01:57:23 PM »
Thank you Oxenkiller. I guess what had me asking is when I look up White Feldspar images, I see a lot of images like the one below which looks similar. So what I gather is is Feldspar has more of a Satin to Powder looking sheen and feel like marble , vs shiny/polished look and hard feeling of quartz? From pics that is all I can pick up if I look closely.


Mark K

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Re: Feldspar, really dumb question
« Reply #3 on: July 13, 2018, 04:55:41 PM »
Vugs are the cavities full of crystals.
Vags are some other type of cavity. We won't go into that here.

HeySal

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Re: Feldspar, really dumb question
« Reply #4 on: July 14, 2018, 06:32:18 AM »
Vugs are the cavities full of crystals.
Vags are some other type of cavity. We won't go into that here.
:o :o :o :o :o ;D ;D ;D ;D ;D

Dereck - feldspar is slightly softer than quartz and can be scratched with a steel file.  You can get sets of hardness points pretty cheaply and they can really help sometimes.
Sal

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dereckc

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Re: Feldspar, really dumb question
« Reply #5 on: July 14, 2018, 05:02:42 PM »
Thank you Sal. I do have a rock hardness scribes, white and dark scratch plates. Just asking for that one special you do to spot a good place to prospect. I know there are clues, just do not recognized as I look. Do not exactly what I am looking for.

Thanks for all the help so far.