However, these natural stone balls are megaspherulites that have been released by erosion from a 20- to 30-million-year-old ash flow tuff, which originally enclosed them and in which they formed.
However, these natural stone spheres originate from megaspherulites that have been exposed through erosion from a 20- to 30-million-year-old ash flow tuff, where they initially formed and were sheltered.