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Andrew Alden

Thrill of the Week: Acasta Gneiss

By May 17, 2011

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acasta gneissMy weekend at CalPaleo 2011 had a good share of thrills, but I think this one may have the most appeal to most of you: I put my hands on one of Earth's oldest rocks, the 4-billion-year-old Acasta Gneiss from northern Canada. It was in Sierra College's wonderful rock walk outside the meeting room. Good old gneiss may be Earth's most distinctive rock. I never used to think much of it because it has no fossils and is difficult to study, but I'm warming up to it as time makes me more metamorphosed.
Acasta gneiss — Geology Guide photo


May 18, 2011 at 6:35 pm
(1) Karen says:

as time makes me more metamorphosed

I know the feeling. :-)

My favorite metamorphic rock is blueschist. I’m a beader as well as a geology student, and my dream beading design is elaborating a seed-bead pattern around a blueschist cabochon… but the jewelry world hasn’t discovered blueschist, and while I live next to a part of the Diablo Range that’s full of it, I’m no lapidary.

So, if you ever see a blueschist cab, blog it, please!

May 18, 2011 at 7:10 pm
(2) Geology Guide says:

I don’t think that blueschist generally takes a good polish, but then I’ve never tried.

May 23, 2011 at 4:14 am
(3) Glen says:

I see this rock often in the field-stones that litter the eastern part of Canada by the millions. Brought down, as you say, from our Far-North. Shaped, ground-down & polished by the glacial-mills of yore. So much ‘silent History?’

May 23, 2011 at 1:47 pm
(4) Geology Guide says:

If I understand Canadian glaciation correctly, the Acasta gneiss would have been carried northwest toward the Arctic Ocean rather than southeast. But Canada certainly has its full share, and more, of extremely old rocks.

May 23, 2011 at 1:52 pm
(5) wally wharton says:

Okay, so we’ve seen the Gneiss, now where’s the Gnephew?

July 9, 2011 at 6:11 pm
(6) Dennis Borden says:

I have made three spheres of this not knowing the age or importance. The rocks were sent to me by a man named Simon from Ontario. He recieved them from a man named Mark from Yellowknife I believe that Mark in turn was to turn the 3.5 inch sphere consisting of three separate colors/ types of rock to the Royal couple. I have not read any of this in accordance to the Royal couples visit though. Mabee the Government kept it instead. Hows That?

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