Long Time Curiosity Rock & Need Help ID broken Points and Matching Tools

[Arsenal]

I have had a rock that has driven me and my friends crazy over the past months. It is a hard stone that is extremely heavy. It shows signs of use or wear and was found in a sandy spot of the San Marcos River. What makes this crazy is it has a line crossing it almost 360 degrees that protrudes out about a centimeter. The line sticking out has some shimmer like some calcite but the rock is not calcite?? Confused yet?

It was difficult photographing and the line hopefully can be seem not as an indention but truly sticking up from the rock. I have never seen anything similar.

I found a few broken points that l am unsure of their name. I am pretty sure one was a Pedernales point but the other longer, thinner one has me miffed. The small dark black flint one, is it even a point? I thought so until I really studied and and concluded I was not positive.

Lastly, hunting the same creeks I find certain tools made certain ways by whatever tribe was there. These two circular scraper types are very common in one creek bed. Is it safe to assume they were made by the same group of people or is there a chance that was just the way they were done in Central Texas at some point?

Thanks to everyone as always.

 

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[Charl]

Your rock shows an example of what is known as differential weathering, described down this page a bit:

Geomorphology_Weathering

The line is a more resistant material then the rest of the rock. Perhaps a layer of quartz. The illustrations show other examples of differential weathering...

 

[The Grim Reaper]

Here's another example of what charl is referring to.

 

[Arsenal]

Thank you very much. That got me thinking and looking at some examples. The main discrepancies is this rock has just one very, very straight line protruding. You are right about the calcite possibility, it just seems to precise on such a smallish hard stone that remains unknown to me. Here is what I think might be an example of your description pictured next to this rock.



I may be way off base. You know how holding a rock is so much different than trying to explain holding a rock? Thanks again, though. I learned something new!!

 

[Arsenal]

GR,

Thanks as always! Your example looks much more similar in that it is a smaller rock. The differences are this rock has a perfectly straight line almost 360 degrees. A small part has been worn away. I found a rock of mine that looks closer to your example than this rock. I pictured them side by side.



Also, it just has a single line. In all of the examples I had found, there were always multiple lines in a more or less haphazard arrangement. I trust your judgement as much as anyone's but thought I would ask your thoughts just the same. Take care.

 

[Charl]

It isn't "one very straight line protruding". It is an entire layer of quartz, both inside the rock, and then protruding out as the softer layers, on either side of the quartz layer, weather. You need to understand that your cobble was once part of a formation many thousands of feet thick. Veins of molten material flowed through that formation, and when they cooled, they became the sheets or layers of quartz within the host rock. Your rock is an example of differential weathering. I left a brief description by posting the link. If you wish to learn more, best bet would be to enroll in a beginner course in physical geology, where you can learn all this is greater detail. Bottom line: your rock is an example of exactly what I told you it was.....

 

[Charl]

Arsenal, I have a background in geology, but I'm not equipped to actually teach geology on a forum. But, an entry level course in physical geology, perhaps at a local college, would certainly allow you to understand this better. You are looking at your rock in isolation, completely devoid of a history that spans millions of years, including when your rock was not a cobble at all, but was part of a distinct rock formation likely thousands of feet thick. Weathering + time= cobbles and pebbles. If you understood that history, and the processes involved in the creation of that formation, including veins of molten material flowing through it episodically, this would be much clearer. But looking at it in isolation as you are doing will only lead you to erroneous conclusions. That quartz vein you see is actually a layer, not simply a skinny vein, it will continue as a sheet within the host rock. The host rock is simply less resistant to weathering, and weathering occurs over time, causing the harder material to stand out, simply because it is more resistant to the weathering involved. There is nothing unusual about this rock.

 

[Arsenal]

Thank you for the clarification. As for taking a geology course to better understand this rock, well, I have this dumb software company that takes up every waking moment. I like learning geology but I also like learning archaeology and anthropology and sociology but I have great respect for geologists. If I can be frank your answer is a little high brow. Are you a teacher? I ask because you address me like a pupil, which I am in a sense, but with the dry nature void of making me think you enjoy this stuff.

Thank you once again for your help. It is appreciated in spite of being turned off by feeling lectured to more than feeling that someone on a forum is trying to help me. Again, I love geology to the extent which time allows. I am pretty sure you mean well, though.

 

[NCPeaches]

Arsenal I'm glad you posted your questions about your rock because Charl and The Grim Reaper's answers really helped me with some that I have found. Your other finds are awesome too

 

[Mrdigz]

Nice Finds!!!
I think Charl was just trying to give you a "crash course" geology lesson on why your rock is the way it is. And it was great advice. Im sure he understands that time hunting artifacts is very valuable so don't waste it on something like a common stone. Since you wrote that it's been driving you guys crazy for months and its sticking out passed the host rock about a centimeter throughout and you were very Confused and you've never seen any other stone like it. He took his time to try and explain why that isn't a very rare occurrence that's all.
I've found many of these rocks myself and If they're cool I will take some home. I'll post whatever I can find that's not in storage or a pain to find.. HH!!!

 

[rock]

Those natural creek rocks are cool in color and design. I got a type that looks worked and is the rite shape of artifacts and points but are natural. They fool me every once in a while still. I will get all happy and put it in my pocket then later I go back through everything I have found and see it was just natural and toss it before I get home. The ones here can be stripped to grey and black.

 

[Arsenal]

Nice Finds!!!
I think Charl was just trying to give you a "crash course" geology lesson on why your rock is the way it is. And it was great advice. Im sure he understands that time hunting artifacts is very valuable so don't waste it on something like a common stone. Since you wrote that it's been driving you guys crazy for months and its sticking out passed the host rock about a centimeter throughout and you were very Confused and you've never seen any other stone like it. He took his time to try and explain why that isn't a very rare occurrence that's all.
I've found many of these rocks myself and If they're cool I will take some home. I'll post whatever I can find that's not in storage or a pain to find.. View attachment 1373782 HH!!! View attachment 1373782 View attachment 1373784 View attachment 1373817 View attachment 1373821

You are spot on and thank you. His delivery of the data was so off-putting that it likely fell on much deafer ears than is usual. It is just as easy to phrase a response like yours. It was positive while explaining in a much easier to understand description. You took my own original questions and addressed them while not belittling me. Go to school and study geology?? I have enough letters after my name and hardly the time to breathe. All that said, I again appreciate your response and agree that your points are completely valid. I realize I am being trite to an extent, we are all works in progress.

 

[rock]

Nice limestone and other rocks