Orthit in den Gesteinen der Sonnblickgruppe (Hohe Tauern)

Some types of Allanite (Orthite) are here described. They are found as assessory minerals in the rocks of the Hohe Tauern (penninic zone of the Eastern Alps) and in the hercynian foreland (Bohemian Massif). We distinguish Allanite I, II and III. The Allanite I (Hohe Tauern) is not isotropisized, but currently idiomorphic, with a xenomorphic rim of Clinozoisite. Where Allanite I is bordering Quartz or Potassium feldspar there is generally no rim of Clinozoisite. In the tectonites one observes granulated Allanite I and transformation of Allanite I to finegranied aggregates of Clinozoisite. Allanite II (Hohe Tauern) is found in intensely radioactive rocks. It is currently isotropisized, xenomorphic and surrounded by xenomorphic rims of Pistacite. Allanite III (Bohemian Massif) may be the oldest one and it is mostly isotropisized. The problems of the genesis and the age of crystallisation of Allanite during the history of our polymetamorphic rocks are shortly touched.