Euendolithic tunnels in flakes on the beach.
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Euendolithic tunnels in flakes on the beach.
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. Showing the euendolithic tunnels in flake Stereo pair euendolithic tunnels in flake 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. Dave
flake in reflected polarised light. Showing the euendolithic tunnels in flake Stereo pair euendolithic tunnels in flake 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. Dave
Last edited by micro_pix on Mon Sep 21, 2020 7:34 am, edited 5 times in total.
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Wow!
Dave, this is most interesting, first time I see these structures.
Dave, this is most interesting, first time I see these structures.
Pau
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
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
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
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
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...
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
I had no idea such things existed. Fascinating!!!
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Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Count me in with the "Beautiful photos!"
--Rik
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.Scarodactyl wrote: ↑Thu Sep 10, 2020 11:03 amThat 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.
--Rik
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Thanks for the comments.
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
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.Scarodactyl wrote: ↑Thu Sep 10, 2020 11:03 amBeautiful 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 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
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Thanks Rick,rjlittlefield wrote: ↑Thu Sep 10, 2020 12:10 pmCount 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
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
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Could you tell us the magnifications you are using?
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Hi Lou,
the second photo is full frame with a 20x objective.
Dave
the second photo is full frame with a 20x objective.
Dave
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
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
Dave
Re: Euendolithic bacteria tunnels in phyllosilicate on the beach.
Here are some more images. There are larger versions in a flickr album here https://flic.kr/s/aHsmQGjVkj.
10x Obj. Polarised 10x Obj. 20x Obj. 50x Obj. 50x Obj. Stereo Suspiciously fungal looking. This is coming towards you from the far plane of the sample, 100x Obj.
10x Obj. Polarised 10x Obj. 20x Obj. 50x Obj. 50x Obj. Stereo Suspiciously fungal looking. This is coming towards you from the far plane of the sample, 100x Obj.
Last edited by micro_pix on Fri Sep 11, 2020 8:08 am, edited 1 time in total.