Sequential opening and filling of cavities forming vesicles, amygdales and giant amethyst geodes in lavas from the southern Paraná volcanic province, Brazil and Uruguay

Léo Afraneo Hartmann; Lauren da Cunha Duarte; Hans-Joachim Massonne; Cassiana Michelin; Leonardo Manara Rosenstengel; Magda Bergmann; Thomas Theye; Juliana Pertille; Karine Rosa Arena; Sandro Kucera Duarte; Viter Magalhães Pinto; Eduardo Guimarães Barboza; Maria Luiza C.C. Rosa; Wilson Wildner