Kyanite

Kyanite bearing micaschist, Bruncu Nieddu.

About 0.5 km further north along the track we reach the kyanite+biotite isograd withmm- to cm-size bluish kyanite crystals in the matrix of the mylonites and in quartz-rich veins (Fig. 1). The kyanite+biotite isograd is marked by the first appearance ofkyanite crystals. The rocks consist of porphyroblasts of staurolite, kyanite, andplagioclase enveloped in a mylonitic matrix of muscovite, biotite, chlorite, and ilmenite. Temperatures up to 595 °C and pressures up to 0.67 GPa have been reported byFranceschelli et al. (1989), and pressures over 0.9 GPa by Carosi & Palmeri (2002) for the metamorphic peak.