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Brushbuffalo
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Brushbuffalo
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PostFri Dec 22, 2017 1:10 pm 
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Thanks for the picture, pcg. Interestingly, I drove by Pueblo Mountain this past July but didn't have time to do any exploring.
The rock appears to be volcanic, probably a tuff breccia made of small rock fragments within a fine-grained matrix. But it could be a pebbly sandstone. I wish I could look at it in hand! 😁  Steens Mountain, a few miles north, is basalt, but the rocks in Nevada and the rest of the  Basin and Range Province are highly varied.
The white mineral is quartz. On the right is milky quartz, which is actually transparent but many microfractures dispersed throughout relect light, giving it the white  appearance.
Over toward the middle and  left are many beautiful euhedral (excellent external crystal form) quartz crystals. Note their elongated prismatic form and on many you can see their hexagonal form on end.
In this rock it is likely that the quartz formed after volcanism produced the igneous rock.
The small  bits of green are some sort of surface vegetation.
Edit: Doppelganger  has a valuable contribution, hypothesizing that the white mineral is natrolite, and I agree. See the posts on  Dec. 28 and Jan. 3.

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pcg
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pcg
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PostSat Dec 23, 2017 10:19 am 
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Thank you. I'm surprised to hear quartz as I've never seen it look like this. If you ever get back to PM and have the vehicle and the nerve to take the road up to Ten Cent Meadow on the west side, that's where I found it, at the high point before heading down to the meadow - all over, even in the road. I'll never travel that road again unless BLM cleans it up with a bulldozer. At some point it will become impassable by even the foolish. Of course you could do the trip on foot as a long day hike as well.
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mike
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PostSun Dec 24, 2017 3:09 pm 
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More of that rock below the summit of Pueblo Mtn. Someone thought it might be worth digging.

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pcg
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pcg
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PostSun Dec 24, 2017 4:05 pm 
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mike wrote:
...Someone thought it might be worth digging.

Yes, that looks like a small quartz deposit. I know there are some old mines/prospect holes on the east side, but we didn't explore that area. I'm curious to know what mineral they were hoping to extract. I'm guessing the sight of the white quartz had them thinking gold might be present?

I think there are opal deposits around as well. I could spend weeks exploring that area.
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Doppelganger
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PostThu Dec 28, 2017 8:30 am 
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pcg wrote:
This stuff is scattered around the top of Pueblo Mountain, in Nevada just south of the Oregon border. The rock is 4" across.


Hmm, I'm probably off on this one too but my first inclination was towards natrolite or gypsum when I saw the radiating sprays and chalky coloration with exposure to the elements. Looking like an unusual (but not impossible!) quartz habit, I noticed the following things that made me wonder:

1. The long thin radiating needles - quartz makes beautiful needles, but I don't recall seeing them in organized clusters or sprays.
2. The central originating points of the sprays (versus the usual "I'll just grow here, and here, and wherever I feel like it" style of quartz)
3. That little round spherule in the center (maybe another on the right edge of mineralization). I think you'll see spherules/bumps in some natrolite pockets that have had some time to grow, but not fill in completely such as this one.
4. Comparing characteristics to these examples of 'massive' natrolite: http://www.johnbetts-fineminerals.com/jhbnyc/mineralmuseum/picshow.php?id=56279

Just my guess, a couple of characteristics here that caught my eye!
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pcg
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PostThu Dec 28, 2017 8:50 am 
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I think a hardness test is in order. I'll do one as soon as I have time to round up a piece of glass.
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Doppelganger
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PostThu Dec 28, 2017 12:18 pm 
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An interesting area for sure, according to this paper the largest mercury mine in the US (as of the paper's publication) was in the vicinity. The paper mentions that zeolite mining has occurred in the area in the past, not sure what the benefits on that might have been - their fragility seems to make them an unattractive candidate for 'collection' mining and I'm not aware of many industrial applications that would make mining for zeolites viable. Page B7 describes one the zeolite prospects as being "3 miles NE of the study area", looking at the map on page B4 it's possible that they refer to the NE slopes of Pueblo Mountain or Ladycomb Peak.

https://pubs.usgs.gov/bul/1740b/report.pdf

However, checking out the real meat of the paper where the contents of the prospects and workings are described, I see that the vast majority produced forms of quartz. Unfortunately the map accompanying the prospect notations doesn't seem to be available, we might have been able to track down the pit in Mike's picture frown.gif
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RichP
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PostThu Dec 28, 2017 8:10 pm 
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This is kind of big, but I'm curious about this formation on Mt Wow on the southwest side of MRNP.


Rock on Mt Wow.
Rock on Mt Wow.
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Nancyann
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PostThu Dec 28, 2017 11:06 pm 
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Brushbuffalo, could you explain what geologic events would cause this giant chasm on Vesper Peak?
Blue Mountain views 12/23/17
Blue Mountain views 12/23/17

And similar ones on Big Four?
Blue Mountain views 12/23/17
Blue Mountain views 12/23/17
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texasbb
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PostFri Dec 29, 2017 7:41 am 
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Nancyann wrote:
Brushbuffalo, could you explain what geologic events would cause this giant chasm on Vesper Peak?
Blue Mountain views 12/23/17
Blue Mountain views 12/23/17

That's obviously evidence of an alien ship crash landing many years ago.  Sometimes they hit wrong and dig trenches.  Sometimes they just scrape and burn the surface:

Don't overlook the obvious. smile.gif

(Actually, I too am interested in knowing what did that to Vesper.)
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Mike Collins
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Mike Collins
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PostSat Dec 30, 2017 6:54 am 
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Nancyann wrote:
Blue Mountain views 12/23/17
Blue Mountain views 12/23/17

The Swauk Formation rock intrudes into a section of the Index batholith here and I am wondering if this line is the border of that intrusion. It looks like a fault line and the North-South directed Straight Creek fault line is in this area too. But I too await Obi Wan Brushbuffalo's input.
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Brushbuffalo
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Brushbuffalo
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PostWed Jan 03, 2018 8:05 pm 
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Doppelganger wrote:
my first inclination was towards natrolite or gypsum when I saw the radiating sprays and chalky coloration

Doppelganger, I wondered about the radiating crystal habit too., unusual for quartz. I am unfamiliar with natrolite but this mineral seems to be an example of it. Thanks for the knowledge.

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Brushbuffalo
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Brushbuffalo
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PostWed Jan 03, 2018 8:15 pm 
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RichP wrote:
This is kind of big, but I'm curious about this formation on Mt Wow on the southwest side of MRNP.


Rock on Mt Wow.
Rock on Mt Wow.

Rich, when seeing layered rocks from a distance you can initially suspect you are observing either sedimentary or volcanic rocks.  Mt. Wow is made of volcanic rocks, much older than Mt. Rainier itself.  In your picture we see many layers. Not having climbed it nor having the geologic map handy right now,  I believe the layers are a complex of lava flows and pyroclastic(fragmental) strata. The prominent reddish zone is probably a zone of highly oxidized iron-rich pyroclastic strata. Note the grayish band within the reddish layers. It is probably a lava flow ( long since cooled, obviously  lol.gif ).. In general in this picture, the wall-like darker gray strata are more resistant than the light gray and tan layers of pyroclastics.

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Brushbuffalo
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Brushbuffalo
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PostWed Jan 03, 2018 8:44 pm 
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Nancyann wrote:
Brushbuffalo, could you explain what geologic events would cause this giant chasm on Vesper Peak?
Blue Mountain views 12/23/17
Blue Mountain views 12/23/17

And similar ones on Big Four?
Blue Mountain views 12/23/17
Blue Mountain views 12/23/17

Nancyann, when you see an arrow-straight feature of size, it is almost always either a fault, a joint (fracture), or a man-made feature. There is a  significant fault (Darrington- Devils Mountain fault zone) extending near the summit of Vesper Peak and there are contacts between three rock formations of contrasting resistance to erosion: granitic rock ( tonalite), metavolcanic rock, and sandstone. Faults and large joints extending  up/down slope often channel surface runoff, and the prominent gash is most likely formed by that process....water running along a zone of weakness (fault, joint, or contact),  thus deepening it.

Edit: find Vesper Peak on Google Earth and zoom in. That gash is very prominent in the image and in it flows the exceptionally straight Stony Creek.

Big Four is composed mainly of metavolcanic rocks. The very steep but not particularly deep valleys on the south aspect of Big Four are due to stream flow but not along any particular zone of weakness. Note how they are rather evenly spaced with ridges intervening.
You can confidently distinguish between stream-eroded valleys (V-shape cross sectional profile) from glacial valleys (U-shaped).

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Nancyann
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PostWed Jan 03, 2018 8:51 pm 
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Thanks for taking the time to answer my question, Brushbuffalo, and Happy New Year!
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