Mica Schist

Mica schist is a shiny metamorphic rock that occurs widely in the Rannoch area. There are two main types of mica, Muscovite and Biotite. Muscovite is transparent whilst Biotite is black. Muscovite gets its name from Moscow where it was once use in windows - Very large crystals are found in Russia. Muscovite has a very high melting point and can be used in furnace windows and as an electrical insulator in domestic irons. The crystals are flat and platey - they can be mixed with paint to form the antifowling paint used on boats' hulls. When barnacles and other sea life tries to attach to the hull the mica flakes off and prevents them from getting a grip. Muscovite is also used as the glitter on Christmas cards.

There is an outcrop of Mica Schist on the Dunalastair estate. It was blasted to expose the rock with a view to starting a commercial mining operation. In the end it was not economic and the attempt was abandoned. The mica schist sparkles and glints in the sunshine on this exposure which lies on the north side of the River Tummel opposite Schiehallion.

The Mica Schist exposure at Dunalastair Estate. The face has been exposed by blasting and the bore holes are visible.

 Muscovite crystal - photo by Rob Lavinsky

Muscovite and Biotite viewed under the microscope.

 Biotite crystals