Mica-schist

The schists are rocks that naturally split off into thin, elongated flakes or slabs. This specimen consists mainly of chlorite and sericite, minerals formed as small, shiny flakes. Therefore, the rock is sometimes called chlorite-sericite schist. Such rocks are formed from fine-grained deposits like clay and sludge that were exposed to high temperature and pressure in the earth’s crust.
Apart from the aforementioned minerals, the specimen contains a group of biotite (black, shiny flakes on the right) and mica (golden flakes). Rusty hues around them resulted from weathering of some of its components.
On the left, scattered like raisins in a cake, there are brown-black garnets, up to 5 mm in diameter.
The right lateral side of the specimen is a cross-section of parallel, several millimetre layers of minerals. Within them there are elongated lenses of grey quartz, 3-4 cm thick.
The rock was formed about 500 million years ago.