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Found here in Newfoundland Canada. I am a newbie at learning this stuff but I have been collecting rocks all my life. Is this pink quartz with mica?

 

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Bits of it are. This is what’s known as pegmatite. It’s a course grained granite. It’s composed of quartz, feldspar, and mica. It sometimes contains beryls and/or tourmalines.

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Posted (edited)
4 hours ago, d_day said:

Bits of it are. This is what’s known as pegmatite. It’s a course grained granite. It’s composed of quartz, feldspar, and mica. It sometimes contains beryls and/or tourmalines.

i appreciate it.  I've been trying to locate pegmatite, but the books say the interlocking crystals are supposed to be an inch.  I've got pegmatite on my claim, at least according to some geological maps, but it looks just like that.  Perhaps its not the size of the crystal that's so important, but the way it interlocks.  Pegmatite is supposed to be good for gems.  This particular pegmatite juts above basalt lava flows.

Edited by chrisski

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Can you tell if it extruded through the basalt, or the basalt flowed around it? I'm curious about that as I have huge lava flows in my area.

Jim

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Posted (edited)

I don't know for sure if the lava flowed around or not. 

The program I have that brings the maps up is for the LSD area, can;t remember the name, but the company was miner diggins.  The incuded geological maps are much more accurate than what the state provides on there website.  There detailed enough to tell the hill 200 meters West of the pegmatite is pre-cambrian metavolvanic and the pagmatite is surrounded by basalt.  To me, pre-cambrian matavolvanic rock means that the hill is excess of 1 Billion years old and had been buried and re-eroded away and is present.  The old timers dug holes about waist deep at a few points in this pegmatite type material, but never took it serious enough to dig a shaft.  I would say the miniers diggins maps had 50 to 100 meter accuracy for the geological formations, but the state site is several hundred meters.

My guess is that the area that has the pegmatite, the basalt flowed around it.  As far as I know, in my local area, although a sign of gems, there are no reported cases of gems in pegmatite in central AZ. I searched anyway hoping to find rubies!  There's some turquoise locally, but no other real semi-precious gem I know of.

Edited by chrisski

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Good ifno...I appreciate that.

Jim

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