<p>If your interested, you can look at the geologic maps for the area on the usgs maps database website:
<a href="https://ngmdb.usgs.gov/ngm-bin/ngm_compsearch.pl" rel="nofollow noreferrer">https://ngmdb.usgs.gov/ngm-bin/ngm_compsearch.pl</a>
You won't be able to download many of them but the site will let you look at them.
I found this for strawberry peak, it's part of the dibblee geo map for chilao quad (7.5'):
<a href="https://i.sstatic.net/gTQsSKIz.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/gTQsSKIz.png" alt="dibblee chilao 7.5' quadrangle" /></a></p>
<p>And here is part of the legend:
<a href="https://i.sstatic.net/I6qtGhWk.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/I6qtGhWk.png" alt="legend to chilao quad" /></a></p>

CC BY-SA 4.0
2024-10-15T22:15:29.767Z
2024-10-15T22:15:29.767Z
Rockmechanic
<p>I'm not a geologist, I am a hiker. And after many hikes in California's Sierra Nevada and Utah's red country I figured it would be great to learn some geology and I'm just posting this question to see if I can get some clarity. Obviously, I don't know what I'm talking about and my experience is limited to reading a book, so I'd very much appreciate your opinion on what I saw on a hike today.</p>
<p>The hike was to strawberry peak (San Gabriel Mountains/Angeles National Forest) looking at rocks and wondering if someone can validate what I think they are :D</p>
<p>I was expecting to see mostly rocks like this - I think this is granite with coarse crystals - igneous rock from down deep in the earth (hand for size reference) - I believe I have this right to call this rock granite? And also that it was formed deep in the earth in a magma chamber and pushed up in whatever episode built these mountains?
<a href="https://i.sstatic.net/SIuQ1.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/SIuQ1.jpg" alt="Is this really granite?" /></a></p>
<p>This also looks like granite, is that correct? What would make the layers and straight lines in this formation? The cracks I believe are from the stresses of the rock getting uplifted and surfaced but I don't know about the lines in the rock itself</p>
<p><a href="https://i.sstatic.net/wY8VJ.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/wY8VJ.jpg" alt="Granite?" /></a></p>
<p>What I was not expecting to see was stuff like this - which seems to me like sedimentary rock because of the layers and the fact that I could very easily pull off straight layers from it without any force at all:</p>
<p><a href="https://i.sstatic.net/EmgnL.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/EmgnL.jpg" alt="Sedimentary?" /></a></p>
<p>Lastly there is what seems like a quartz vein inside this sedimentary(?) rock, is this just another layer of the rock or what type of process could inject quartz (or whatever this is) into the rock?</p>
<p><a href="https://i.sstatic.net/KVSBo.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/KVSBo.jpg" alt="enter image description here" /></a></p>
<p>Thank you in advance!</p>

CC BY-SA 4.0
2022-05-28T08:42:54.157Z
The layers look like a foliation to me, a feature typical of metamorphic rocks.
Jean-Marie Prival
CC BY-SA 4.0
2022-05-29T00:02:18.680Z
Ah interesting. I’ll have to read about that. I did see some layers that were in bent shapes so perhaps there was so metamorphosis going on
Amperie 
CC BY-SA 4.0
2022-05-29T11:20:08.773Z
Yes, these can be metamorphic granitoids, but I would rather think that these are gneisses.
Weiss
CC BY-SA 4.0
2024-10-09T03:52:42.377Z
It looks like a felsic gneiss.
Matt Mulder
<geology><rocks><mountains><igneous><orogeny>
Geology of the San Gabriel mountains in the Angeles national forest - rock types
Amperie 
# Geology of the San Gabriel mountains in the Angeles national forest - rock types

(Asked by: username_0 on 2022-05-28)

I'm not a geologist, I am a hiker. And after many hikes in California's Sierra Nevada and Utah's red country I figured it would be great to learn some geology and I'm just posting this question to see if I can get some clarity. Obviously, I don't know what I'm talking about and my experience is limited to reading a book, so I'd very much appreciate your opinion on what I saw on a hike today.

The hike was to strawberry peak (San Gabriel Mountains/Angeles National Forest) looking at rocks and wondering if someone can validate what I think they are :D

I was expecting to see mostly rocks like this - I think this is granite with coarse crystals - igneous rock from down deep in the earth (hand for size reference) - I believe I have this right to call this rock granite? And also that it was formed deep in the earth in a magma chamber and pushed up in whatever episode built these mountains?
[![Is this really granite?](https://i.sstatic.net/SIuQ1.jpg)](https://i.sstatic.net/SIuQ1.jpg)

This also looks like granite, is that correct? What would make the layers and straight lines in this formation? The cracks I believe are from the stresses of the rock getting uplifted and surfaced but I don't know about the lines in the rock itself

[![Granite?](https://i.sstatic.net/wY8VJ.jpg)](https://i.sstatic.net/wY8VJ.jpg)

What I was not expecting to see was stuff like this - which seems to me like sedimentary rock because of the layers and the fact that I could very easily pull off straight layers from it without any force at all:

[![Sedimentary?](https://i.sstatic.net/EmgnL.jpg)](https://i.sstatic.net/EmgnL.jpg)

Lastly there is what seems like a quartz vein inside this sedimentary(?) rock, is this just another layer of the rock or what type of process could inject quartz (or whatever this is) into the rock?

[![enter image description here](https://i.sstatic.net/KVSBo.jpg)](https://i.sstatic.net/KVSBo.jpg)

Thank you in advance!

**Tags:** geology, rocks, mountains, igneous, orogeny

> **Comments:**
> **username_1**: The layers look like a foliation to me, a feature typical of metamorphic rocks.  
> **username_0**: Ah interesting. I’ll have to read about that. I did see some layers that were in bent shapes so perhaps there was so metamorphosis going on  
> **username_2**: Yes, these can be metamorphic granitoids, but I would rather think that these are gneisses.  
> **username_3**: It looks like a felsic gneiss.  

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## 1 answers

### Answer by username_4 on 2024-10-15. Score: 1

If your interested, you can look at the geologic maps for the area on the usgs maps database website:
<https://ngmdb.usgs.gov/ngm-bin/ngm_compsearch.pl>
You won't be able to download many of them but the site will let you look at them.
I found this for strawberry peak, it's part of the dibblee geo map for chilao quad (7.5'):
[![dibblee chilao 7.5' quadrangle](https://i.sstatic.net/gTQsSKIz.png)](https://i.sstatic.net/gTQsSKIz.png)

And here is part of the legend:
[![legend to chilao quad](https://i.sstatic.net/I6qtGhWk.png)](https://i.sstatic.net/I6qtGhWk.png)


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