Cerasite

Right crystal: 10 mm long. Cerasite in hornfels. Cerasite is cordierite and indialite crystals replaced by muscovite or paragonite. There is a hexagonal prism of indialite at the center of the cerasite, and cordierite grew over the indialite core. Indialite is a hexagonal dimorph of cordierite and is stable at higher temperature than cordierite. The two dispached hexagonal prisms at the right indicate the shape of cordierite overgrown on the hexagonal indialite prisms. The cross section are shown in the left specimen. As this cross section is near the edge of cerasite prism, indialite hexgonal prism core is not shown. The black host of the right specimen is weathered hornfels.

Recovered from hornfels formed by hornblende-hornfels facies contact metamorphism of S-type (Ilmenite-series) granodiorite. Formed in the Late Cretaceous (95 Ma).

Cerasite from this location was described in 1979, and was designated the prefectural mineral of Kyoto in 2016 by the Geological Society of Japan.