Biotite <a href="https://en.wikipedia.org/wiki/Dacite" class="extiw" title="en:Dacite">dacite</a> from Dunabogdány, Hungary. This rock is of Miocene age, formed 15 million years ago. This rock is on display at the Hungarian rocks collection at Hegyestű geopark, Hungary.
Szilas
Photo by Szilas