For the science enthusiasts among us, I present sakura ishi, the “cherry-blossom stone.”
Dr. John Rakovan of Miami University (Ohio) has published work on these stones which occur in Kameoka, Kyoto Prefecture.
Science Alert describes them as
So-called because when you crack them open, their internal cross-sections look like tiny golden-pink flowers, cherry blossom stones (sakura ishi in Japanese) get their beautiful patterns from mica, which is a commonly found silicate mineral known for its shiny, light-reflecting surface.
These flower patterns weren’t always made of mica. They started their existence as a complex matrix of six prism-shaped crystal deposits of a magnesium-iron-aluminium composite called cordierite, radiating out from a single dumbbell-shaped crystal made from a magnesium-aluminium-silicate composite called indialite in the centre.
“Although the sakura are ephemeral in their beauty, lasting only a few weeks each year,” says Rakovan, “their image has been set in stone in the sakura ishi of Kameoka.”