In the Southern Carpathians, metamorphic rocks dominate. They are formed at high temperature and/or high pressure by recrystallization of previously formed rocks in their solid phase. The temperature and pressure at which this transformation took place are indicated by the mineral association of the metamorphic rock. In the vicinity of Sebeşu de Sus, kyanite-containing metamorphites are common for example. Kyanite is an aluminosilicate (Al₂SiO₅), the presence of which suggests that the host rock was formed from argillaceous sediments at high pressure (usually above 4000 bar – for comparison atmospheric pressure is 1 bar).
In the picture: Kyanite, Sebeşu de Sus, Romania. Size: 15 cm. Photo by Géza Kulcsár