photomicrographs FKM-1 to FKM-20

 

The images presented here are grouped photomicrographs of selected representative, distinctive, or simply photogenic regions from the samples presented in the thin section scans pages.

Each image set consists of a plane-polarized light (PPL) photomicrograph (taken using the default E-W lower polarizer alignment), a potential second PPL photomicrograph taken with the lower polarizer rotated to a N-S alignment if notable variations in mineral pleochroism or relief warrant this additional view, and finally a photomicrograph taken under crossed polarizers (XP).

Preceding each set of images is table of diagnostic optical features specific to the accompanying images, to aid viewers differentiate the key minerals in the images. Note that in some cases, not every mineral present will be noted in the table or on the photomicrograph (particularly for material that is very fine-grained, very finely intergrown with other minerals, or grains that may simply be too small or too sparse). For the same reasons, not every mineral listed in the thin section scans composition tables will be included here either.

Due to the potential wealth of images (and to keep page loading times reasonable), each photomicrograph page will only feature 20 samples. This page and additional photomicrograph pages will be a new website feature I’m working on, and so these pages will be very much under construction. Check back periodically as I add more images and tables.

 




diagnostic mineral properties observable in FKM-1 ROI 1

mineral look for this in the PPL image look for this in the XP image
graphite E-W: opaque
calcite high order creamy-buff birefringence
grossular E-W: high relief; nearly colorless; similar to zoisite isotropic
titanite E-W: high relief; medium brown high order creamy-buff birefringence masked by brown color
zoisite E-W: high relief; nearly colorless; similar to grossular 1st order white birefringence with slight anomalous blue tint
diopside 2nd order blue birefringence
quartz E-W: low relief; colorless 1st order gray to yellowish-white birefringence
tsavorite and tanzanite in thin section Merelani Tanzaniatsavorite and tanzanite in thin section Merelani Tanzania

FKM-1 ROI 1; left image: PPL with E-W lower polar (50X); right image: XP (50X)


diagnostic mineral properties observable in FKM-1 ROI 2

mineral look for this in the PPL image look for this in the XP image
calcite high order dark creamy-buff birefringence
grossular E-W: high relief; nearly colorless; similar to zoisite isotropic
zoisite E-W: high relief; nearly colorless; similar to grossular 1st order white birefringence with slight anomalous blue tint
quartz E-W: low relief; colorless 1st order dark gray to white birefringence
tsavorite and tanzanite in thin section Merelani Tanzaniatsavorite and tanzanite in thin section Merelani Tanzania

FKM-1 ROI 2; left image: PPL with E-W lower polar (50X); right image: XP (50X)


diagnostic mineral properties observable in FKM-1 ROI 3

mineral look for this in the PPL image look for this in the XP image
calcite high order creamy-buff birefringence
grossular E-W: high relief; nearly colorless; similar to zoisite isotropic
titanite E-W: high relief; medium brown high order creamy-buff birefringence masked by brown color
zoisite E-W: high relief; nearly colorless; similar to grossular 1st order white birefringence with slight anomalous blue tint
diopside 2nd order blue birefringence
quartz E-W: low relief; colorless 1st order dark gray to light gray birefringence

Merelani Tanzania tsavorite in thin section

Merelani Tanzania tsavorite in thin section

top image: PPL with E-W lower polar (50X)
bottom image: XP (50X)

 




diagnostic mineral properties observable in FKM-2 ROI 1

mineral look for this in the PPL images look for this in the XP image
titanite E-W: high relief; v. pale buff pleochroism
N-S: high relief; pale buff pleochroism
high order cream birefringence
piemontite E-W: high relief; yellow, orange, red & magenta pleochroism
N-S: high relief; orange, red & purplish-red pleochroism
birefringence masked by strong coloration
quartz E-W: low relief; colorless
N-S: low relief; colorless
1st order gray to white birefringence

St Marcel Italy piemontite in thin section

St Marcel Italy piemontite in thin section

St Marcel Italy piemontite in thin section

top image: PPL with E-W lower polar (50X)
middle image: PPL with N-S lower polar (50X)
bottom image: XP (50X)


diagnostic mineral properties observable in FKM-2 ROI 2

mineral look for this in the PPL images look for this in the XP image
titanite E-W: high relief; v. pale buff to medium brown pleochroism
N-S: high relief; v. pale buff to medium brown pleochroism
high order dark cream birefringence
piemontite E-W: high relief; orange, red & magenta pleochroism
N-S: high relief; orange, red & purplish-red pleochroism
birefringence masked by strong coloration
quartz E-W: low relief; colorless
N-S: low relief; colorless
1st order white birefringence

St Marcel Italy piemontite in thin section

St Marcel Italy piemontite in thin section

St Marcel Italy piemontite in thin section

top image: PPL with E-W lower polar (50X)
middle image: PPL with N-S lower polar (50X)
bottom image: XP (50X)