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PostPosted: Fri May 10, 2019 9:09 am 
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Red Sea sand is rich in colorful minerals (granite rocks), foraminifera and other shells and things. The collected sample underwent wet sieving, washing with tap water and distilled water, then drying in an oven at 170C for 1h. The narrow grain size range makes a thin, uniform layer in the Petri dish, and facilitates the treasure hunt. Interesting forms were picked out at the stereoscope, under 10X total magnification, using a wetted fine-tip painter's brush, or even better, a fine syringe needle (size 23G, 0.6mm diameter). Larger grains (>1mm) were easily picked with jeweler's forceps. I mounted them in chamber slides, where a 13mm-diameter, 2mm deep circular chamber was created by punching out a 2.5cm wide, 2mm thick double-sided adhesive tape (a well-known trick). The tape is affixed on top of the slide, and the chamber can be topped with a square coverslip. Such a chamber is almost too thick for the working distance of my Zeiss 6.3X Plan objective, so a thinner tape might be better. The grain forms are mounted within the chamber onto a thin layer of PVA-based office glue.

Epi-illumination on the compound microscope was achieved with two 5mm super-bright LEDs, diagonally directed below the objective front lens. This was a cheap and space saving arrangement for the 6.3X objective. The condenser top, under the stage, was covered with black velvet cloth, rather than black cardboard. Photos were taken with Canon camera. Stacked with PICOLAY.

Among the grains are white flat porous fragments and discs (photos 3, 4). Pore size is 8-35 microns. Are they coral skeletons? There is a nearby reef. Help with identification - welcome!

Forams were white or yellow or beige (a black one escaped my forceps). Dilute citric acid dissolved the calcium carbonate, so the white form disappeared, but the yellow form left over some thin brown-black strands and thin membranes, presumably organic. I might pre-clean the sample with peroxide.


Attachments:
(1) Red Sea sand, grain size 0.7-2mm, phone camera.jpg
(1) Red Sea sand, grain size 0.7-2mm, phone camera.jpg [ 452.02 KiB | Viewed 651 times ]
(2) Sample of photo 1, USB camera on sterescope, 10X, field width 10mm.jpg
(2) Sample of photo 1, USB camera on sterescope, 10X, field width 10mm.jpg [ 191.35 KiB | Viewed 651 times ]
(3) Sample of photo 1,  USB camera on sterescope, 24X, field width 4mm. 1- foraminifera, 2 - unknown, 3 - mica, 4- quartz.jpg
(3) Sample of photo 1, USB camera on sterescope, 24X, field width 4mm. 1- foraminifera, 2 - unknown, 3 - mica, 4- quartz.jpg [ 193.02 KiB | Viewed 651 times ]
(4) Forams and unknown porous fragments,  USB camera on sterescope, 24X, field width 4mm.jpg
(4) Forams and unknown porous fragments, USB camera on sterescope, 24X, field width 4mm.jpg [ 321.44 KiB | Viewed 651 times ]

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PostPosted: Fri May 10, 2019 9:10 am 
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(Continued) Note: Photo 5 was taken under trans-illumination through the Ph3 phase contrast position of the condenser, the 6.3X Plan is non-phase objective. So, it is darkfield, the aperture condenser was closed to illuminate only the center of the FOV.


Attachments:
(5) Foram, trans-illumination, 6.3X0.16 Plan, stack of 3, 900 micron.jpg
(5) Foram, trans-illumination, 6.3X0.16 Plan, stack of 3, 900 micron.jpg [ 32.24 KiB | Viewed 650 times ]
(6) As photo 5 but epi-illumination, single image.JPG
(6) As photo 5 but epi-illumination, single image.JPG [ 92.34 KiB | Viewed 650 times ]
(7) Same sample as in photo 6, improved light, stack of 5.jpg
(7) Same sample as in photo 6, improved light, stack of 5.jpg [ 35.02 KiB | Viewed 650 times ]
(8) Stack of 5.jpg
(8) Stack of 5.jpg [ 34.92 KiB | Viewed 650 times ]

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PostPosted: Fri May 10, 2019 9:17 am 
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Location: NorthWest England
Nice work ... and your "(2) Sample of photo 1, USB camera on sterescope, 10X, field width 10mm.jpg" is very effective.

MichaelG.

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PostPosted: Fri May 10, 2019 9:30 am 
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Thanks MichaelG.

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PostPosted: Fri May 10, 2019 9:38 am 
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Location: Cumbria, UK
A superb set of crisp images and a very nicely put-together presentation.
This is a great example of what's 'out there' for those with a little curiosity and a will to follow it up!
Your description of the processing and 'scope techniques used is very interesting and informative, thanks for a very nice post indeed

Look forward to more of this quality. :)

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PostPosted: Fri May 10, 2019 10:18 am 
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Thanks John B! More ideas about the sand are being pondered...

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PostPosted: Fri May 10, 2019 2:32 pm 
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Hi Doron,
thank you for posting these beautiful images! I like the trans illuminated images best with it's warm glow.

Sand is a nice topic to demonstrate the value of microscopy - one gets a better understanding of the world around without much effort. I like to look at beautiful things and sand offers a lot if observed in detail.

Foraminifera are useful in scientific sense as they allow to determine the change of coast lines over the time.

Bob


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PostPosted: Fri May 10, 2019 2:40 pm 
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Very nice post and pics, thanks! I've been looking at local beach sand under the stereo scope too. I need to keep experimenting. Here is a sample.

The clear is quartz, pink is garnet (some with inclusions), black are iron/metal oxides. Brown looks like root beer soda bottle:)


Attachments:
long island beach sand.jpg
long island beach sand.jpg [ 196.83 KiB | Viewed 618 times ]
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PostPosted: Fri May 10, 2019 7:05 pm 
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MicroBob wrote:
...Foraminifera are useful in scientific sense as they allow to determine the change of coast lines over the time.
Thanks Bob! I am reading that Foraminifera are now considered important indicators and sensors of global climate changes, since their building of the shells ("tests") depends on CO2 level in the oceans, on the marine water acidity, etc.

geo_man wrote:
The clear is quartz, pink is garnet (some with inclusions), black are iron/metal oxides. Brown looks like root beer soda bottle:)
Thanks geo_man. Agreed about the root beer. Luckily my samples appear to be devoid of anthropogenic articles.
Here is a way to isolate iron oxides: I keep my pieces of neodymium magnet within a plastic test-tube, for safety reasons, since they are very strong magnets indeed. I wiped it along the heap of sand, and, lo and behold, several 3mm size grains, probably of iron oxide (magnetite), were attracted to the test-tube and attached to it, so picked out of the heap. An "ordinary" magent of the same size is not sufficiently powerful to extract the magnetite from the sand.


Attachments:
Magnetite particles from the sand, attracted to magnet.jpg
Magnetite particles from the sand, attracted to magnet.jpg [ 104.8 KiB | Viewed 600 times ]

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PostPosted: Fri May 10, 2019 7:18 pm 
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Thanks Hobbyst46, i will look into that!!

And of course, forms can be used to date ancient strata.


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PostPosted: Tue May 14, 2019 1:14 am 
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Beautiful foram images, keep 'em coming!

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PostPosted: Tue May 14, 2019 2:53 pm 
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Thanks KurtM. I am still working on it...

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PostPosted: Thu May 16, 2019 9:38 am 
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Changes to illumination and chamber:

I thought that a complete 60mm-diamater LED ring, placed around the objective, would provide better epi-illumination of the sand and forams, and experimented. Yet, the pair of 5mm diameter, super-bright warm-white LEDs, symmetrically positioned at opposing points and beaming obliquely, better accentuates the patterns on the grain surface. Here is a scheme of the setup. Each LED is supported by a small ramp (shown in green), made of aluminum plates, and is affixed to the sloping plate with adhesive, sticky tape, clay etc. The ramps are laid on the stage and can be moved and nudged for optimum illumination. Primitive, yet flexible. The condenser top lens is shaded with black velvet cloth

For the chambers, I now use 1mm-thick double-sided adhesive tape. The chamber is thin enough for easy observation with my 6.3X/0.16 Plan and 10X/0.30 Neofluar objectives. A coverslip is used to protect both the objective and specimen.

Mica fragments:
I had fractionated my sample of sand by sieving. The finest grain fraction, of size <0.7mm, contained golden, semi-transparent shining platelets, which I think are Mica. They are thin, flat and very weakly birefringent. Below are photos of some of them, of sizes 400/900 micrometer, recorded with 10X/0.30 objective and illuminated either by the oblique epi-LEDs, or by brightfield+polarizer. Post processing: Resized, uniformly cropped and tweaked contrast.
Comments are welcome.


Attachments:
(9) Epi-oblique illumination.jpg
(9) Epi-oblique illumination.jpg [ 58.19 KiB | Viewed 426 times ]
(10) Stack of 2, epi-oblique.jpg
(10) Stack of 2, epi-oblique.jpg [ 51.97 KiB | Viewed 426 times ]
(11) Stack of 2, epi-oblique.jpg
(11) Stack of 2, epi-oblique.jpg [ 27.37 KiB | Viewed 426 times ]
(12) Stack of 3, epi-oblique.jpg
(12) Stack of 3, epi-oblique.jpg [ 30 KiB | Viewed 426 times ]

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PostPosted: Thu May 16, 2019 9:41 am 
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(continued)


Attachments:
(13) Stack of 3, BF+POL (angle A).jpg
(13) Stack of 3, BF+POL (angle A).jpg [ 64.22 KiB | Viewed 425 times ]
(14) Stack of 4, BF+POL (angle B).jpg
(14) Stack of 4, BF+POL (angle B).jpg [ 62.31 KiB | Viewed 425 times ]
(15) Stack of 4, BF+POL.jpg
(15) Stack of 4, BF+POL.jpg [ 55.08 KiB | Viewed 425 times ]

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