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A nice Fall day in the Sacramento Mountains


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I decided to get out for what might have been the last warm day in the 70's (Farenheit) for a walkabout to explore high country access and exit points for some long climbs I would like to do this winter.

 

For this trip I rucked primarily in the lower Pennsylvanian formations looking specifically for a new occurrence of mineral rich shale formations similar to one I had found last year that yielded plant fossils. I did manage to find a small but new-to-me location that was very geologically complex having anomalies in the midst of the shale/sandstone formations.

 

First this Cordaite about 5" tall (12.5 mm)

 

cordaite.thumb.jpg.e9c99071a783b4a379764b5f67de0be4.jpg 

 

Quite near were numerous Liesegang specimens. This one about 2" x 2" (5mm x 5mm)

 

liesegang.thumb.jpg.63b2d0c00748b8518377e918ef866b86.jpg

 

There seemed to be at least two small areas where hot gasses may have vented through the field leaving small seams of quartz-like material. 

 

In one location samples present as Bornite. The largest piece below is 3" x 6" (7.5mm x 15.5mm)

peacock2.thumb.jpg.fc75df9da4eae5e63eb52a42b8475e75.jpg

 

The other area was just at the contact zone between the shale having plant fossils and sandstone having plant fossils. This specimen seems to have mostly converted the sandstone and permineralized material into quartz. There is a small specimen of permineralized material left in the lower right corner. Also, there is some mineralization which I believe is mostly iron.

 

outgas2.thumb.jpg.2d18cd3866417f57dfabd58095e4b790.jpg

 

As this new location is about 4.5 miles from where I parked my vehicle I did not collect many specimens (small pack) but plan to go back and spend more time searching.

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Above the previously mentioned sandstone formation was a small layer of shale that appeared to be somewhat altered by an igneous layer of Camptonite above it. 

 

This small piece of shale yielded a small fossil I need to research. The shale is so hard I can't reveal anymore of the item. At first I thought it might be a seed pod but am not committed to that.  It is about 0.5" at the longest revealed dimension (1.5mm)

 

pod1.thumb.jpg.85efafaf4924c3eca799a5bcd12fcce5.jpg

 

Some distance away in a limestone formation I found this geologic oddity. It appears to be a mish-mash of items of which I am not even certain if what I first thought was crinoids is indeed crinoids as the columnals would be unlike any I've seen before.

 

5dd6d0de850a1_StrangeOverall.jpg.5de45a0cc4a6fc668847a07157c408a8.jpg

 

Here is a closer view of the 3 possible crinoid columns at the top of the previous picture. I neglected to actually measure the longest one but, by recollection, believe it was about 7" long (18mm).

 

5dd6d10a89509_Strange3tentacles.thumb.jpg.cfdf05223a985f10a9a5450277a03319.jpg

 

Regardless, if nothing special, it was fun to find and admire. 

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I'd say you're looking at some ichnofossils there, rather than crinoids.

 

F3.large.jpg.   F8.large.jpg

 

 

 

 

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4 hours ago, Fossildude19 said:

I'd say you're looking at some ichnofossils there, rather than crinoids.

 

F3.large.jpg.   F8.large.jpg

@Fossildude19      

 

Thank you!

 

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Nice ichnofossils. :)

Interesting report and photos, I love the bornite. 

 

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FranzBernhard
12 hours ago, Kato said:

In one location samples present as Bornite.

I am more inclined that these are manganese oxide or hematite coatings with iridescent surface.

Some tests would be required: 

- What happens if you put a fragment in a flame? Did you get a pungent/stinging smell of SO2?

- How does a fresh break look like? Bornite would be metallic pinkish, turning to red and blue within hours.

@ynot

Franz Bernhard

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1 hour ago, FranzBernhard said:

I am more inclined that these are ..... hematite coatings with iridescent surface.

Bornite does not form botryoidal structures so the piece in question is not that mineral.

It does look like iridescent hematite to Me also.

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7 hours ago, FranzBernhard said:

I am more inclined that these are manganese oxide or hematite coatings with iridescent surface.

Some tests would be required: 

- What happens if you put a fragment in a flame? Did you get a pungent/stinging smell of SO2?

- How does a fresh break look like? Bornite would be metallic pinkish, turning to red and blue within hours.

@ynot

Franz Bernhard

@FranzBernhard @ynot

 

Thank you. Hematite seems the most likely candidate given the geology of that immediate area. I had just taken some 40x magnification shots and it definitely is botryoidal.

 

Given that recommendation I did some research and found the possibility of Turgite a mixture of hematite and goethite. Apparently there is an entire hillside exposed somewhere in New Mexico.

 

 

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