Need help identifying this rock, Found in northern MN

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In summary, the image is not visible for me. If you need help getting your image to post, let us know. We can help.
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  • #2
The image is not visible for me. If you need help getting your image to post, let us know. We can help.
 
  • #3
@jim mcnamara it looks like he was able to upload it now.

@ReevesN76R -- Welcome to the PF. Can you take a closeup picture of the marks on the rock? Are those marks (like drawn), or are they something embedded?
 
  • #5
berkeman said:
@jim mcnamara it looks like he was able to upload it now.

@ReevesN76R -- Welcome to the PF. Can you take a closeup picture of the marks on the rock? Are those marks (like drawn), or are they something embedded?
They are embedded.
 

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The porphyritic basalt seems to be correct. I have been collecting rocks and minerals for 55 years.
 
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  • #9
Cool rock.
 
  • #10
a rhombic porphyry most likely - how come you found it in Minesota, tough? They are more common in the scandinavian region around Oslo, Norway. :wink:
 
  • #11
GeologyRocks1909 said:
how come you found it in Minesota
The rock is rounded and river worn, so it was not taken directly from an outcrop. It has probably been carried by a glacier or an ice sheet during the last glacial period. It may have traveled a long way south from some volcanics in Canada.
I have found identifiable rocks in unexpected places, but only where glaciation was available to transport them.
 
  • #13
It looks like what I have known as a "pudding stone"
 
  • #14
gleem said:
It looks like what I have known as a "pudding stone"
Pudding stone is a sedimentary "conglomerate" of rounded pebbles in a fine matrix. It looks like a cut slice through a plum pudding.

The rock pictured was volcanic, having a fine green basalt matrix with large phenocrysts of feldspar. A rock with phenocrysts is described as a porphyry, or as being porphyritic. The phenocrysts are crystallised out of the melt over many years as the magma gradually rises up towards a volcanic vent. The fine grained matrix indicates that it cooled quickly once it reached the surface which is why it is known to be a volcanic rock.
https://en.wikipedia.org/wiki/Phenocrysts
 
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  • #15
Does the rock have any value?
 
  • #16
As is, not really worth much.

If you like rock cutting and polishing, it would sell for a fair amount after it was polished on a cut through the middle.
Go to a local natural history museum store or one of the places that sell display quality minerals. You can get a good idea. Some mineral collectors use a rock tumbler only to polish. No cut.

My wife did this for fun and the results were amazing.
 
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1. What type of rock is this?

This is a common question when identifying a rock. In order to accurately determine the type of rock, it is helpful to know its physical characteristics such as color, texture, and mineral composition. It may also be helpful to use a field guide or consult with a geologist.

2. Where was this rock found?

The location of where the rock was found can provide important clues to its origin and composition. For example, rocks found near a volcano may be different from rocks found in a riverbed. It is important to note the location when identifying a rock.

3. Is this rock valuable?

The value of a rock can vary greatly depending on its rarity, beauty, and potential uses. Some rocks may have industrial uses, while others may have value as collectibles. It is best to consult with a professional or do some research to determine the value of a rock.

4. How old is this rock?

Determining the age of a rock can be a complex process, as it involves understanding geological processes and using various dating techniques. Some common methods include radiometric dating and relative dating based on the rock's placement in the geological timeline. A geologist may be able to provide a more accurate estimate of a rock's age.

5. What can this rock tell us about the environment it was found in?

Rocks can provide valuable information about the environment in which they were formed. The type of rock, its mineral composition, and its location can all give insights into the past climate, geologic processes, and even the presence of certain organisms. A thorough examination and analysis of the rock can help us better understand the environment it was found in.

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