🔎 UNIDENTIFIED What is this strange rock marking and how did it happen?

RSMITH

Greenie
Jul 22, 2013
10
16
Denver, Colorado
Primary Interest:
Prospecting
Hey Everyone,

Last fall, I was prospecting in Clear Creek Canyon along US 6 And found something interesting.

I was working an old dried up gravel bench where the river used to flow, and several feet down behind a large boulder, I spotted this bizarre "notched" rock in the hole.

I cannot figure out for the life of me: Who? What? How? Why? Lol
The walls of the indententation in the rock have PERFECT planes. What's most peculiar is that the bottom of the indentation is PERFECTLY flat as well.
If this was indeed made by a chisel, first of all, why? And if it was chiseled, how in the Michaelangelo did the bottom of the indentation become perfectly flat and planed? Almost like it was laser cut! The rough walls of the indententation on right and left sides made me suspect Chisel, but I don't understand how one would achieve such smooth planes. Why this rock? Why do this and then huck it into the river?

I've been staring at this rock on my desk for months wondering about it. Any insight or ideas as to what it might be, or what it's purpose is would be awesome! Thank you!
 

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Solution
That's neat. I would guess that a large tabular mineral crystal has dropped out of the matrix, having been loosened by erosion. Given the granitic appearance, feldspar would be a strong possibility.

Feldspar.jpg

Almy

Bronze Member
Mar 18, 2011
1,046
1,911
Maritime Provinces
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Tesoro Cibola
Primary Interest:
Other
Kinda looks like granite. Tombstone engravers can produce the kinds of planes seen in your sample.
 

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RSMITH

Greenie
Jul 22, 2013
10
16
Denver, Colorado
Primary Interest:
Prospecting
That's neat. I would guess that a large tabular mineral crystal has dropped out of the matrix, having been loosened by erosion. Given the granitic appearance, feldspar would be a strong possibility.

View attachment 2134018
I used this info to look up several more examples and I believe you hit the nail on the head! Wow! Thank you, Sir. How cool. I wonder how many decades or eons earlier I would have needed to find it to still have the crystal attached 😂
Regardless, really appreciate the insight and definitely something I'll keep in my "cool to me, but otherwise useless" treasure box.
 

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Robot

Bronze Member
Mar 10, 2014
2,005
1,695
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Hi RSMITH,
I am not a gold prospector, but I have seen many pictures of them hitting stones with their Rock Hammer looking for gold deposits within.
I believe your stone is granite a very hard stone and was known to contain gold samples within it at Clear Creek Canyon.
This was the location of the first Gold Deposits in Colorado.
Clear Creek Canyon is cut into highly resistant granite and gneiss bedrock, originally formed deep beneath ancient mountain ranges 25 million years ago.
The mountains in Colorado contain many hard rock lode deposits which are gold-bearing veins and also ore bodies that are typically found in granite, quartz monzonite, and other igneous rocks within the area.

Could your stone have a Chisel Mark left in it by a Gold Prospector using his Rock Hammer Chisel End?

Rock Hammer 2.jpg
Rock Hammer.jpg
 

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