ChristopherHuey
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Plagioclase
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(Original post by ChristopherHuey)
Any help?

It appears to be a sandstone. Mostly quartz (up to 90%), with some possible feldspar (10%). Grain size 0.0625 - 2 mm. Medium to coarse grained. Rounded (quartz) to sub-angular (feldspar) grains. No cleavage for the quartz. Two cleavages for the feldspar: one perfect, one good, approximately at right angles. Bedform is likely cross-bedding. More mature than immature.

Does this seem reasonable based on the attachments/links provided?
I would not be comfortable making any kind of detailed description from photos alone without having a hand specimen. There's no scale so I'm going to assume your size description is correct, although if you're saying it's coarse-to-medium grained then your size bracket would be 0.25-1mm. It does seem like there's some feldspar there although I can't tell what proportion it is (that white stuff looks a bit like weathered plag, maybe there's some k-feldspar too because of the pink? Not sure). From the photos, I'd very tentatively say that the sorting looks reasonable, but you're in the best position to make that judgement since you have the rock. I can't make out any bedforms, where are you seeing those? It's probably somewhere between mature and immature, if your guess about the feldspar proportion is correct and the quartz grains are indeed rounded then I'd probably agree with you.

Edit: If you need more help, then you could give /r/geology a go, they've helped me out with thin sections before.
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Reality Check
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(Original post by Plagioclase)
I would not be comfortable making any kind of detailed description from photos alone without having a hand specimen. There's no scale so I'm going to assume your size description is correct, although if you're saying it's coarse-to-medium grained then your size bracket would be 0.25-1mm. It does seem like there's some feldspar there although I can't tell what proportion it is. From the photos, I'd very tentatively say that the sorting looks reasonable, but you're in the best position to make that judgement since you have the rock. I can't make out any bedforms, where are you seeing those? It's probably somewhere between mature and immature, if your guess about the feldspar proportion is correct and the quartz grains are indeed rounded then I'd probably agree with you.
It's taken me about a year to connect your name with the word 'feldspar' and guess your subject area... :facepalm:
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Plagioclase
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(Original post by Reality Check)
It's taken me about a year to connect your name with the word 'feldspar' and guess your subject area... :facepalm:
Haha, got there in the end!
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Reality Check
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(Original post by Plagioclase)
Haha, got there in the end!
- hopeless, aren't I. And I enjoyed Geology, particularly a field trip to the Isle of Arran. Maybe if your name had been 'Gneiss' I might have got there sooner! Oh well...
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username2088165
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(Original post by Reality Check)
- hopeless, aren't I. And I enjoyed Geology, particularly a field trip to the Isle of Arran. Maybe if your name had been 'Gneiss' I might have got there sooner! Oh well...
My own experience of a field trip to Arran was a nightmare :lol:
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username2088165
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#7
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(Original post by ChristopherHuey)
Hi All,

I know it's difficult to say too much without access to the specimen, as that and further diagnostic testing is necessary to make an accurate description of a rock.

However, I would appreciate your input on what you think regarding the attached images.

I have also posted links to the images which allow you to zoom in and see much more detail than the attached images (which have been sized down to fit the requirements).

Link to image 1: https://drive.google.com/file/d/0B23...ew?usp=sharing

Link to image 2: https://drive.google.com/file/d/0B23...ew?usp=sharing

Link to image 3: https://drive.google.com/file/d/0B23...ew?usp=sharing

Link to image 4: https://drive.google.com/file/d/0B23...ew?usp=sharing

I am interested in description such as colour, mineralogy, grain size, sorting, sphericity, etc.. All descriptive input is welcomed.

Thanks for your time,

Chris
I should say that I'm a lot more confident with thin sections than hand specimens (especially seeing as my sedimentology lecturer was awful), but I'll have a go

Colour: beige, brown and white
Mineralogy: quartz, feldspar (not sure about % of each)
Grain size: hard to tell without a scale, but it looks fairly coarse so possibly coarse to very coarse sand (approx 1-2mm)
Sorting: probably moderately sorted
Sphericity: hard to see, but I would guess rounded to sub-angular
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Reality Check
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(Original post by Leviathan1741)
My own experience of a field trip to Arran was a nightmare :lol:
My memories (non-geological) include hard bunk beds in the field centre, rain, flasks of coffee, special 'pads' of a sort of plastic/rubbery paper that you could use in the rain with a pencil and discovering Drambuie. And the ferry over - in about a force 9 severe gale. But with the passage of time they've become very fond memories!
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username2088165
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(Original post by Reality Check)
My memories (non-geological) include hard bunk beds in the field centre, rain, flasks of coffee, special 'pads' of a sort of plastic/rubbery paper that you could use in the rain with a pencil and discovering Drambuie. And the ferry over - in about a force 9 severe gale. But with the passage of time they've become very fond memories!
My memories include having quite possibly the worst sore throat I've ever had, terrible pea soup, wind and rain, 'freeze-thaw' showers, and nearly falling backwards off a cliff
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Flying Lotus
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Is there any particular reason you're doing this with pictures as opposed to in the lab, where I presume lab assistants/lecturers are available to help you in person? It's really difficult to help, apologies.

To echo the sentiment of Plagioclase, I too am not very comfortable with trying to classify a blurry photo of a hand specimen.
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