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Let's Rock => Ancient Lapidary History => Topic started by: Kaljaia on May 09, 2016, 12:05:47 PM

Title: Speaking of Patinas
Post by: Kaljaia on May 09, 2016, 12:05:47 PM
A broken stone found in a ditch beside a road.

(https://67.media.tumblr.com/3c91e68f1640cc063f1a472f462c243f/tumblr_o6xgajG1gu1spns93o1_1280.jpg)
(https://65.media.tumblr.com/a7ab13ee651e5ba75fe360e1d4a00dd0/tumblr_o6xgajG1gu1spns93o2_1280.jpg)
(https://67.media.tumblr.com/2629e3c0c7a418ef712b9656aedbc324/tumblr_o6xgajG1gu1spns93o3_1280.jpg)

Very distinct difference in patina between sides. Flat grinder, I think? It was in a pretty clearly disturbed area and looked like it had been driven over, so not of historical value- well displaced from whatever location and strata it would have come from.
As to the patina, I am curious to know how many strokes it would take to polish and shine a stone that much. Would a good grinding stone be carried from camp to camp? Passed down from one generation to the next? Were they 'seasoned' by use and considered more valuable the smoother they got, or less effective as the rough surface wore off?

Or is it just the result of natural weathering?
Title: Re: Speaking of Patinas
Post by: Enchantra on May 09, 2016, 12:16:25 PM
I am going to say this is a product of weathering.  One side more exposed than the other.
My archaeological knowledge from studying Native artifacts in college and grad school tells me this is not man made.
Title: Re: Speaking of Patinas
Post by: Kaljaia on May 09, 2016, 12:35:13 PM
I am going to say this is a product of weathering.  One side more exposed than the other.
My archaeological knowledge from studying Native artifacts in college and grad school tells me this is not man made.

Thanks for the response! I'll compare it to other local rock and see if the patina is replicated, maybe from a local wildfire. The road is not traveled enough for it to be 'cobblestone' wear. Would water produce such an uneven effect? 
Title: Re: Speaking of Patinas
Post by: lithicbeads on May 09, 2016, 01:10:01 PM
I assume there was a photo with this post but it is not showing for me.
Title: Re: Speaking of Patinas
Post by: Kaljaia on May 09, 2016, 01:48:19 PM
I assume there was a photo with this post but it is not showing for me.

Thanks for letting me know! I swapped image hosting. Do they show up now?
Title: Re: Speaking of Patinas
Post by: lithicbeads on May 09, 2016, 05:48:11 PM
Yes and the stone looks extremely well worn. I suspect just a few years could do that because the stone they ground on became worn as well. All the grit was not good for the teeth at all.
Title: Re: Speaking of Patinas
Post by: brentnewton on February 21, 2019, 03:35:21 PM
Geological time is vast :) It strains the mind to understand.  Its not a man-made artifact .. its an artifact of time.  Vast time ... deep time. Most cobbles .. have been worked a lot of times. Over and over. And .. over.  I am in KY and have a ... serious interest in Pennsylvanian fluvial conglomerates .... lol.  Um ... think about 300 million year ago. I look at a cobbles and wonder where the hell in half a freaking continent it came from - if the continents were anywhere near where the a now (not) ... its a bit of a puzzle .. ok .. more than a bit of a puzzle.  Sure as heck ... ain't man made ya know .... just my thing ya know.  The continents were no where close to where they were ... mountains were .. nothing like are now .. deep time ... and we didn't talk about environments or atmosphere yea now.  Climate change meh ....
Title: Re: Speaking of Patinas
Post by: GoodEarth on February 25, 2019, 10:26:28 AM
Desert Varnish accounts for the patina.
Title: Re: Speaking of Patinas
Post by: lithicbeads on February 25, 2019, 07:06:43 PM
A forensic geologist gave me a good lesson once. I took him to a remote canyon to see an unbelievable boulder the size of a cabin. After he looked at it for a while I asked him where he thought it came from hoping to find the in situ source. He looked at me and pointed straight up and said , " About 3,000 feet that way". The rock was so dense that any stream ever in that drainage would not have been strong enough to move it but as the stream eroded it's surroundings it move toward the center of the earth. It is easy to forget about the now largely absent third dimension of our geological trips. In Washington very old large streams are often responsible for water worn stones and even fairly large sections of old river beds perched on canyon walls. New streams cut the old river beds . In Washington and Idaho these ancient stream beds can be  a wonderful source of ancient alluvial gold as often false bedrock is easily seen in the eroded stream profiles. Let your imagination go out there.