Plane polarised light

Cross polarised light

Kyanite Gneiss. The rock specimen was taken from a hillside about 400m. ENE of Craigoshina, Glen Esk, Grampian Region, NO575766 by Brian Young. It consists mainly of kyanite and micas, predominently muscovite.
The high relief and strong "railway line" cleavage of kyanite is readily seen centre and towards the bottom right of the specimen in plane polarised light. The green mineral with a radiating structure, seen towards the right could be a type of mica or possibly chlorite. For scale, the dark "triangle" seen towards the right is 2mm. in length.

Created with Memory-Map. ©Crown Copyright. Licence number 100034184.

The above photograph shows the bright interference colours of muscovite, especially towards the left. The dark patche at the top right is a hole in the thin section.
Kyanite is an aluminium silicate, which, like andalusite and sillimanite, develops in aluminium rich pelites (metamorposed mud/siltstones) under different conditions of temperature and pressure.

Top of page
Back to thin section thumbnails