Sedimentary Rock or Man-made?

[DanFL1962]

Yesterday I was hiking along the Slippery Rock Gorge in Western PA and found these stones.

Any idea if they are sedimentary rock or perhaps just aggregate from an old piece of sidewalk?

Thanks,
Dan

 

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[MinerGirl]

Hi Dan. When I first looked at your post I thought the pics looked just like Chatahochee Rock. I know I spelled it wrong but Google... Images under that spelling. It sure looks like the first pic on that page and your rocks look very much like the rocks they use as "Pool Decking", only pool decking is pretty when they combine the rock with the epoxy? that glues the decking in place. I see you are also from Brevard County, Fl? Thats where my Dad lives and he's a Geologist...I will ask him when I see him and post his reply. Might be awhile though...

 

[DanFL1962]

Hi Dan. When I first looked at your post I thought the pics looked just like Chatahochee Rock. I know I spelled it wrong but Google... Images under that spelling. It sure looks like the first pic on that page and your rocks look very much like the rocks they use as "Pool Decking", only pool decking is pretty when they combine the rock with the epoxy? that glues the decking in place. I see you are also from Brevard County, Fl? Thats where my Dad lives and he's a Geologist...I will ask him when I see him and post his reply. Might be awhile though...

Thanks MinerGirl. Yes, it does resemble that Chatahochee. My first thought was man-made but after looking at it for a while, I'm thinking its part of the Glacial till that is so prominent in this area. Although these two pieces were unique, compared to everything else I saw yesterday.

 

[MinerGirl]

Hi again, I have a quick question. Have you ever Metal Detected in Sebastian Inlet, (Brevard County) before the bridge there? When I was a senior in High School I remember finding about 10 pieces of "pieces of eight". I was pretty excited and told my Dad there must be a Sunken Ship straight out from that beach. Of course he just laughed. A few years later is when they found that Ship and was one of the biggest treasures found. (One of the 12 ships that sank in the Hurricane of the 1700's) Anyway, I'm sure there's lots of detecting that can be done that is not in the "no detecting" areas there.

 

[DanFL1962]

Oh yes. Sebastian is one of my favorite areas. I lived in Brevard/Orange Counties for 10+ years, now its rare for me to get down there. But I love detecting the treasure coast. You should post your Pieces of Eight on the Beach and Shallow Water forum here. People are still finding artifacts from from that fleet.

 

[Eu_citzen]

Looks sedimentary, is it pretty solid and tough to break apart? Conglomerate might be a candidate.

 

[DanFL1962]

Looks sedimentary, is it pretty solid and tough to break apart? Conglomerate might be a candidate.

Yes, definitely "rock" solid. Thanks!

 

[DanFL1962]

Yesterday I sent an inquiry to the Pennsylvania Dept of Natural Resources and just heard back from them.

[FONT=&quot]"Those are neither glacial nor man-made. They are fragments of the Homewood sandstone, which forms the cliffs above the Mill down past Breakneck Bridge, across the creek from where you collected these. The cliffs also exist above where you collected them on the northwest side of the creek. The Homewood sandstone has some pebbly layers. Next time you’re at the Mill, look at the cliffs along the walkway from the parking lot at the top down to the Mill. You’ll see the sandstone in place that looks very similar to these samples.[/FONT]

[FONT=&quot] [/FONT]
[FONT=&quot]The Homewood sandstone actually dies out very close to where you collected these samples. Just a short way below Eckert Bridge, the sandstone pinches out, and the interval is all shale.[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]The samples are just pieces that have weathered out from the cliffs above. They may have moved downstream some, but they are fairly angular, so have probably not been transported very far.[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]If you look at the Park Guide we have written for Moraine and McConnells Mill State Parks at Pennsylvania Geological Survey: Park Guide 4 - Pebbly layers, you’ll see a photo of the Homewood sandstone that looks very much like your samples, taken near the Mill.[/FONT]"