Euendolithic tunnels in flakes on the beach.

Images made through a microscope. All subject types.

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micro_pix
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Euendolithic tunnels in flakes on the beach.

Post by micro_pix »

I took a small sand sample from a beach in Dorset, UK the other day. It's mostly quartz grain sand and I was hoping to find some foraminifera, I did but I also found that there were lots of phyllosilicate (mica) flakes in the sample. The flakes were up to 3mm long and varied in thickness, they looked pretty under reflected polarised light but they had an unusual pattern on the surface. The appearance of the pattern reminded me of the patterns made by the endolithic cyanobacteria I saw on oolite sand grains from the Bahamas so I played around with the lighting a little and the tunnels through the mica, presumably left by the bacteria, are easily visible. The thin white geometric lines are the edges of the plates in the mica.

flake in reflected polarised light.
Mica flake reflected polarised
Mica flake reflected polarised
Showing the euendolithic tunnels in flake
Euendolithic bacteria tunnels
Euendolithic bacteria tunnels
Stereo pair euendolithic tunnels in flake
Stereo pair of euendolithic bacteria tunnels in mica
Stereo pair of euendolithic bacteria tunnels in mica
A larger stereo pair on Flickr https://flic.kr/p/2jFagju

Here are some of the other finds - up to about 2mm - I don't know what the club/microphone shaped object is.
forams etc.
forams etc.
Dave
Last edited by micro_pix on Mon Sep 21, 2020 7:34 am, edited 5 times in total.

Pau
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by Pau »

Wow!
Dave, this is most interesting, first time I see these structures.
Pau

micro_pix
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by micro_pix »

Hi Pau,

I’d seen these bacteria tracks in ooids viewtopic.php?f=14&t=36436&hilit=Oolite but they are calcium carbonate, as are the mollusc shells they also tunnel in to. Maybe they like the iron content of the mica but silicates are harder to dissolve than carbonates if they use an acid.

Dave


Scarodactyl
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by Scarodactyl »

Beautiful photos! That said I wouldn't discount these being inclusions of another mineral. I have seen this kind of shape in curved needle inclusions in other minerals. There has been a suggestion of bacterial etching in garnets before but it's been met with a lot of skepticism and it's still contentious. On the other hand we've all seen what fungus can do to glass...

Lou Jost
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by Lou Jost »

I had no idea such things existed. Fascinating!!!

rjlittlefield
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by rjlittlefield »

Count me in with the "Beautiful photos!"
Scarodactyl wrote:
Thu Sep 10, 2020 11:03 am
That said I wouldn't discount these being inclusions of another mineral. I have seen this kind of shape in curved needle inclusions in other minerals.
I suppose it's a silly question, but has biological origin of the curved needle inclusions been ruled out? Knowing nothing about those cases, it's easy for me to imagine biological burrows getting re-filled with deposits of a different mineral.

--Rik

micro_pix
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by micro_pix »

Thanks for the comments.
Scarodactyl wrote:
Thu Sep 10, 2020 11:03 am
Beautiful photos! That said I wouldn't discount these being inclusions of another mineral. I have seen this kind of shape in curved needle inclusions in other minerals. There has been a suggestion of bacterial etching in garnets before but it's been met with a lot of skepticism and it's still contentious. On the other hand we've all seen what fungus can do to glass...
I was just applying what I’d learn’t from the oolitic sand and it’s endolithic bacteria as the tunnels looked very similar and the same sort of size.

I did see the paper on the Garnet in Thailand, the tubes look a bit different, they were narrow funnel shaped and branching. I emailed the author to ask if he could shed any light on this sample, hopefully he’ll get back. These tubes do look rather biological but having seen the effort to try and confirm the Garnet theory, with all of their resources......

I did read about bacterial etching on volcanic glass on the ocean floor too.

A high proportion of the tiny flakes from the sample of sand I took have the same phenomena, I was thinking that either they are all from the same larger piece (unlikely) or the tunnelling/inclusions happened when they were already flakes in the ocean. Does that make any sense and would that make mineral inclusion unlikely.

I really know nothing about geology so I’m going to look at mica formation, I’ll probably find that it all looks like this under the microscope!

Dave

micro_pix
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by micro_pix »

rjlittlefield wrote:
Thu Sep 10, 2020 12:10 pm
Count me in with the "Beautiful photos!"

I suppose it's a silly question, but has biological origin of the curved needle inclusions been ruled out? Knowing nothing about those cases, it's easy for me to imagine biological burrows getting re-filled with deposits of a different mineral.

--Rik
Thanks Rick,

what is documented with the ooids in the Bahamas is that the tunnels are back filled with more precipitated CaCO3 (because that is what the water is saturated with) but it is of a different structure and makes the tunnels distinguishable under light and even fluorescence microscopy.

Dave

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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by Saul »

Impressive stereo !
Saul
μ-stuff

Lou Jost
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by Lou Jost »

Could you tell us the magnifications you are using?

micro_pix
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by micro_pix »

Hi Lou,

the second photo is full frame with a 20x objective.

Dave

micro_pix
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by micro_pix »

I have been contacted by a scientist I sent the photos to and he has said that they may have been produced by hyphal fungi rather than bacteria; I’m going to post a few flakes to him so that he can look at them on a micro CT scanner. Meanwhile I’m going to take some more photos.

Dave


micro_pix
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.

Post by micro_pix »

Here are some more images. There are larger versions in a flickr album here https://flic.kr/s/aHsmQGjVkj.

10x Obj. Polarised
mica_874.jpg
10x Obj.
mica_bw.jpg
20x Obj.
mica_redriuh.jpg
50x Obj.
mica_95945.jpg
50x Obj. Stereo
mica_stereo_55-Edit.jpg
Suspiciously fungal looking. This is coming towards you from the far plane of the sample, 100x Obj.
mica_457er56.jpg
Last edited by micro_pix on Fri Sep 11, 2020 8:08 am, edited 1 time in total.

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