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Author Topic: What's this rock? Looks volcanic?  (Read 1803 times)

Offline mysteryrock

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What's this rock? Looks volcanic?
« on: 07/08/2014 19:10:34 »
Hey everyone, long time reader, first time poster.
I found this rock about six years ago here

newbielink:https://www.google.com/maps/preview?q=silver+lake+ct&ie=UTF-8&ei=K7zjU8HtE879yQSCjYGYAg&ved=0CAYQ_AUoAQ [nonactive]

buried in the mud. It looks like quartz veins that got squished into some shale maybe? I only took one geo class in college but this one looks interesting enough to keep. If anyone needs more pictures, please let me know. The veins have very small crystals, and are orange/clear in color. The bottom has maybe marble, or something? It is very white. Perhaps quartzite? Anyone who cannot see the map, it is of Sharon CT. Maybe this location would help, as I know it went through some volcanic activity at some point.

Thank you fellow scientists!

newbielink:https://plus.google.com/photos/116399624881149166086/albums/6044884294802860897?authkey=CMOB6_CorbvPHA [nonactive]

The outside link is because I wanted high quality pictures. Thanks for understanding.


 

Offline Bass

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Re: What's this rock? Looks volcanic?
« Reply #1 on: 07/08/2014 23:52:13 »
Great pictures!  And being into mineral exploration, this is my kind of rock.

My take is that this is banded quartz veins.  Even more interesting is the "drusy" quartz along some of the veins and the variety of oxidation colors.  Drusy quartz only forms in cavities or openings, which means this had to be fairly shallow when the quartz veins formed (if you get very deep, the pressures from the overlying rock won't allow cavities to form).  There is a white mineral that is interbanded with the quartz, possibly feldspar (adularia?), or less likely calcite.  Adularia is a common mineral in certain, shallow (epithermal) ore deposits.  The oxidation colors suggest jarosite (yellowish), hematite (reddish) and possibly realgar (orange)- suggesting this was possibly mineralized with pyrite (iron sulfide) and arsenopyrite (iron-arsenic sulfide). Additionally, in a couple of the photos, small vugs (or boxwork) are visible that was almost certainly metallic sulfide minerals at one time.
Many of the bonanza gold and silver ores (high grade ores) in Nevada have a similar banded appearance with ozidized  iron and arsenic sulfide minerals.
The surrounding rock is fairly high grade metamorphic rock- which means that this specimen had to survive high heat and pressure, suggesting deep burial after it formed.  Fascinating that it retained the "shallow" texture.
Are there any mines in the vicininty?
« Last Edit: 07/08/2014 23:56:53 by Bass »
 

Offline mysteryrock

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Re: What's this rock? Looks volcanic?
« Reply #2 on: 08/08/2014 03:24:08 »
Wow! Thank you for the long description. Reayy interesting. I found a few examples of quartzite mining, and this if you want to take a read:

newbielink:http://www.sharonhist.org/sharon-iron-industry.htm [nonactive]
 

Offline Bill S

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Re: What's this rock? Looks volcanic?
« Reply #3 on: 19/08/2014 21:28:50 »
Great pictures and great explanation.  All I can add is that looking at those pics makes me feel homesick for my native Cornwall and its fascinating geology.  :(
 

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Re: What's this rock? Looks volcanic?
« Reply #3 on: 19/08/2014 21:28:50 »

 

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