Pumpellyite, prehnite - retrograde minerals of Ca-skarns of Bratislava massif

The brick massif of Bratislava is linked to amphibolites, which can be found in three localities: Zelezna Studnicka, Velka Bana, Zahorska Bystrica. High-temperature bricks have been affected by retrograde reactions, most often metasomatic. These processes formed the secondary minerals pumpellyite and prehnite in the metamorphic basemente. The pumpellyite of the Bratislava Massif is of the Al-type type (Al₂O₃ content 24 to 27.5 wt.%) and is divided into two groups according to variations in the iron content. Prehnite is a rare mineral that forms fibrous crystals in direct association with biotite that intergrows it. It is characterized by small chemical variations. PT conditions of the Bratislava aureole were at the value up to 3.5 kbar and 550-650 grad C. (authors)