Introduction - Geomaterials: Under the Microscope - page 6

7

This is termed 'fluorescence microscopy' and Figures 7
and 8 show a comparison between a rock sample in
cross-polarized light and fluorescent light, illustrating
how the fluorescence view defines porous areas.
Sometimes highly polished specimens are prepared for
examination in reflected light (brightfield and darkfield).
Reflected light is particularly useful for examination of
opaque minerals and cements. Figures 9 and 10 show a
comparison of ore minerals shown in transmitted light
and reflected light. Each of the plate captions in this topic
includes an abbreviation to show the viewing light of the
photomicrograph as follows:
Applied light Abbreviation

Plane-polarized transmitted PPT

Cross-polarized transmitted XPT

8

Plane-polarized reflected PPR

Cross-polarized reflected XPR

Normal reflected NR

Reflected fluorescence UV

Each photomicrograph caption also includes the viewing
magnification which correspond to the following fields of
view:
Magnification Approximate field of view (mm)

× 35 4.5

× 75 2.5

× 100 1.8

× 150 1.0

× 200 0.8

7, 8 Fluorescent yellow resin impregnated thin-section
specimen of marble. Viewed in cross-polarized
transmitted light ( 7 ) and in reflected fluorescent light
( 8 ); ×150.

× 300 0.5

× 600 0.2

9 10

9 Roofing slate in thin section viewed in plane-
polarized transmitted light. Inclusions of pyrite appear
opaque (black); PPT, ×75.

10 Highly polished specimen of roofing slate viewed
in reflected light. Inclusions of pyrite reflect light
(yellowish-white); XPR, ×75.