Hey Alex, @alex-rosas, thank you so much for the pictures. Now I am quite sure that this is a nice example of a gap filling. The gap space was perfect for crystallization of quartz out of a silicate rich fluid. The crystals have enough space to grow and they grow all from the same origin (the edge of the gap) into the free space. That is my interpretation. Any thoughts from my colleagues @smoran, @vperez, @egardner ?