Sample EC96-001 -- thin section results

This document presents transmitted light images of a thin section from the specimen of "Carboniferous human bone" sent by Ed Conrad for evaluation -- specimen EC96-001. These images were made using a video capture setup attached to a Wild Photomakroskop M400 and a Leitz Orthoplan petrographic microscope. Unfortunately the video capture hardware has lower resolution than traditional photographic techniques, but I was trying to save the cost of film and processing, and the resolution is more than sufficient for this exercise.

NOTE: Some of these images are quite large. Check the sizes before downloading.

Reflected light images

The thin section was made within a few millimetres of the surface illustrated in reflected light in Figs.5-9 on the other page about EC96-001. For comparison, here is one of the images:

Fig.1 -- reflected light image for comparison (296Kbytes). Magnification: approximately 6.5x.

Transmitted light images (from thin section)

Fig.2 -- portion of thin section (113Kbytes) , showing general appearance. Transmitted, plane polarized light (PPL). Blue material is dyed epoxy resin used as a mounting media. Outlined box on right corresponds to the location of Fig.4. Outlined box on left corresponds to Fig.14. This image was digitally reconstructed from a mosaic of images captured from video. Magnification: approximately 6.6x.

Fig.3 -- lower left area of Fig.1 (42Kbytes). PPL. Magnification: approximately 10x.

A note about magnification

The images below were photographed (captured) on the Leitz photomicroscope. Ed appears to prefer using the magnifications engraved on the microscope optics when comparing the size of structures, so I have provided those values here. However, even at a display resolution of 92 pixels per inch, most of these images have a higher effective magnification. For example, on my 92 ppi display, the image photographed at 128x actually represents a 280x increase over the original size (the 100 micron scale bar is 28 millimetres long). I leave it as an exercise for the reader to calculate the effective magnification for their own screen setup.

Below the "rectangular structure"

Fig.4 -- to lower left of rectangular opaque structure (39Kbytes). Circled areas are around noteable transparent structures, some of which are shown at higher magnification in subsequent figures. Magnification: photographed at 20x. Effective magnification will be greater, depending upon your display.

Fig.5 -- crossed nichols (XN) (43Kbytes). Enlargement of the upper part of Fig.4. Magnification: photographed at 50.4x.

Fig.6 -- PPL (42Kbytes) Fig.7 -- crossed nichols (XN) (34Kbytes) Fig.8 -- rotated 40 degrees to show variations in interference colours and extinction. XN. (36Kbytes) Figures 6-8 are an enlargement of the lower left circled area of Fig.4. Fig.6 is in plane polarized light, and looks much as would be observed in normal (unpolarized) light. Fig.7 and 8 are in "cross nichols", where the polarizer and analyzer of a petrographic microscope are at 90 degrees to eachother. If a mineral is anisotropic -- i.e. different light speeds through the crystal lattice depending upon orientation -- the emerging light rays will interfere to produce colours or darkness depending upon the orientation of the mineral and its optical properties. Compare Fig.7 and 8 -- some of the light-coloured, nearly transparent structures in Fig.7 are black ("extinct") in Fig.8, which has been rotated 40 degrees with respect to Fig.7. Amongst other things, this phenomena makes it possible to distinguish transparent voids (i.e. holes) from transparent mineral grains. Holes filled with isotropic mounting media are isotropic, and are black in crossed nichols at all orientations. Anisotropic, transparent crystals "blink" on and off as they are rotated. Magnification: photographed at 128x.

Fig.9 -- Same location as Figs.6-8. (35Kbytes). PPL. Fig.10 -- Same location as Figs.6-9. (29Kbytes) XN. Magnification: photographed at 200x.

Fig.11. (22Kbytes) PPL. Note greenish grain (circled) with foliated structure. Fig.12 -- Same location as Figs.6-11 (20Kbytes), right of Figs.9-11. XN. Note the spectrum of interference colours observed on the circled grain. Magnification: photographed at 504x.

Fig.13 -- Same location as Figs.6-12 (22Kbytes), lower left of Figs.9-11. XN. Magnification: photographed at 504x.

Near the left edge

Fig.14 -- Rectangular outlined area at lower left edge of Fig.1. (34Kbytes) Magnification: photographed at 50.4x.

Fig.15 -- Same location as Fig.14. (41Kbytes) PPL. Magnification: photographed at 128x

Comparison

Fig.16 -- comparison of EC96-001 (left) and dinosaur bone (right) (92Kbytes). PPL. EC96-001 image corresponds to Fig.5 (except that this one is in PPL). Magnification: photographed at 50.4x.

Fig.17 -- comparison of EC96-001 (left) and dinosaur bone (right) (64Kbytes). XN (left) PPL (right). EC96-001 image corresponds to Fig.7. Magnification: photographed at 128x.

Fig.18 -- comparison of EC96-001 (left) and dinosaur bone (right) (67Kbytes). PPL. EC96-001 image corresponds to Fig.15. Magnification: photographed at 128x.

Back to the evaluation of Carboniferous bone

Andrew MacRae macrae@geo.ucalgary.ca